When restoring a reservation for an anonymous page, we need to check to
freeing a surplus. However, __unmap_hugepage_range() causes data race
because it reads h->surplus_huge_pages without the protection of
hugetlb_lock.
And adjust_reservation is a boolean variable that indicates whether
reservations for anonymous pages in each folio should be restored.
Therefore, it should be initialized to false for each round of the loop.
However, this variable is not initialized to false except when defining
the current adjust_reservation variable.
This means that once adjust_reservation is set to true even once within
the loop, reservations for anonymous pages will be restored
unconditionally in all subsequent rounds, regardless of the folio's state.
To fix this, we need to add the missing hugetlb_lock, unlock the
page_table_lock earlier so that we don't lock the hugetlb_lock inside the
page_table_lock lock, and initialize adjust_reservation to false on each
round within the loop.
Link: https://lkml.kernel.org/r/20250823182115.1193563-1-aha310510@gmail.com
Fixes: df7a6d1f64 ("mm/hugetlb: restore the reservation if needed")
Signed-off-by: Jeongjun Park <aha310510@gmail.com>
Reported-by: syzbot+417aeb05fd190f3a6da9@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=417aeb05fd190f3a6da9
Reviewed-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Breno Leitao <leitao@debian.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
There is a comment in hugetlb_fault() that does not hold anymore. This
one:
/*
* vmf.orig_pte could be a migration/hwpoison vmf.orig_pte at this
* point, so this check prevents the kernel from going below assuming
* that we have an active hugepage in pagecache. This goto expects
* the 2nd page fault, and is_hugetlb_entry_(migration|hwpoisoned)
* check will properly handle it.
*/
This was written because back in the day we used to do:
hugetlb_fault () {
ptep = huge_pte_offset(...)
if (ptep) {
entry = huge_ptep_get(ptep)
if (unlikely(is_hugetlb_entry_migration(entry))
...
else if (unlikely(is_hugetlb_entry_hwpoisoned(entry)))
...
}
...
...
/*
* entry could be a migration/hwpoison entry at this point, so this
* check prevents the kernel from going below assuming that we have
* a active hugepage in pagecache. This goto expects the 2nd page fault,
* and is_hugetlb_entry_(migration|hwpoisoned) check will properly
* handle it.
*/
if (!pte_present(entry))
goto out_mutex;
...
}
The code was designed to check for hwpoisoned/migration entries upfront,
and then bail out if further down the pte was not present anymore, relying
on the second fault to properly handle migration/hwpoison entries that
time around.
The way we handle this is different nowadays, so drop the misleading
comment.
Link: https://lkml.kernel.org/r/20250627102904.107202-5-osalvador@suse.de
Link: https://lkml.kernel.org/r/20250630144212.156938-5-osalvador@suse.de
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Gavin Guo <gavinguo@igalia.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "Misc rework on hugetlb faulting path", v4.
This patchset aims to give some love to the hugetlb faulting path, doing
so by removing obsolete comments that are no longer true, sorting out the
folio lock, and changing the mechanism we use to determine whether we are
COWing a private mapping already.
The most important patch of the series is #1, as it fixes a deadlock that
was described in [1], where two processes were holding the same lock for
the folio in the pagecache, and then deadlocked in the mutex. Note that
this can also happen for anymous folios. This has been tested using this
reproducer, below
Looking up and locking the folio in the pagecache was done to check
whether that folio was the same folio we had mapped in our pagetables,
meaning that if it was different we knew that we already mapped that folio
privately, so any further CoW would be made on a private mapping, which
lead us to the question: __Was the reservation for that address
consumed?__ That is all we care about, because if it was indeed consumed
and we are the owner and we cannot allocate more folios, we need to unmap
the folio from the processes pagetables and make it exclusive for us.
We figured we do not need to look up the folio at all, and it is just
enough to check whether the folio we have mapped is anonymous, which means
we mapped it privately, so the reservation was indeed consumed.
Patch#2 sorts out folio locking in the faulting path, reducing the scope
of it ,only taking it when we are dealing with an anonymous folio and
document it. More details in the patch.
Patch#3-5 are cleanups.
Here is the reproducer:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/wait.h>
#define PROTECTION (PROT_READ | PROT_WRITE)
#define LENGTH (2UL*1024*1024)
#define ADDR (void *)(0x0UL)
#define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB)
void __read(char *addr)
{
int i = 0;
printf("a[%d]: %c\n", i, addr[i]);
}
void fill(char *addr)
{
addr[0] = 'd';
printf("addr: %c\n", addr[0]);
}
int main(void)
{
void *addr;
pid_t pid, wpid;
int status;
addr = mmap(ADDR, LENGTH, PROTECTION, FLAGS, -1, 0);
if (addr == MAP_FAILED) {
perror("mmap");
return -1;
}
printf("Parent faulting in RO\n");
__read(addr);
sleep (10);
printf("Forking\n");
pid = fork();
switch (pid) {
case -1:
perror("fork");
break;
case 0:
sleep (4);
printf("Child: Faulting in\n");
fill(addr);
exit(0);
break;
default:
printf("Parent: Faulting in\n");
fill(addr);
while((wpid = wait(&status)) > 0);
if (munmap(addr, LENGTH))
perror("munmap");
}
return 0;
}
You will also have to add a delay in hugetlb_wp, after releasing the mutex
and before unmapping, so the window is large enough to reproduce it
reliably.
: --- a/mm/hugetlb.c
: +++ b/mm/hugetlb.c
: @@ -38,6 +38,7 @@
: #include <linux/memory.h>
: #include <linux/mm_inline.h>
: #include <linux/padata.h>
: +#include <linux/delay.h>
:
: #include <asm/page.h>
: #include <asm/pgalloc.h>
: @@ -6261,6 +6262,8 @@ static vm_fault_t hugetlb_wp(struct vm_fault *vmf)
: hugetlb_vma_unlock_read(vma);
: mutex_unlock(&hugetlb_fault_mutex_table[hash]);
:
: + mdelay(8000);
: +
: unmap_ref_private(mm, vma, old_folio, vmf->address);
:
: mutex_lock(&hugetlb_fault_mutex_table[hash]);
This patch (of 5):
hugetlb_wp() checks whether the process is trying to COW on a private
mapping in order to know whether the reservation for that address was
already consumed. If it was consumed and we are the ownner of the
mapping, the folio will have to be unmapped from the other processes.
Currently, that check is done by looking up the folio in the pagecache and
compare it to the folio which is mapped in our pagetables. If it differs,
it means we already mapped it privately before, consuming a reservation on
the way. All we are interested in is whether the mapped folio is
anonymous, so we can simplify and check for that instead.
Link: https://lkml.kernel.org/r/20250630144212.156938-1-osalvador@suse.de
Link: https://lkml.kernel.org/r/20250627102904.107202-1-osalvador@suse.de
Link: https://lkml.kernel.org/r/20250627102904.107202-2-osalvador@suse.de
Link: https://lore.kernel.org/lkml/20250513093448.592150-1-gavinguo@igalia.com/ [1]
Link: https://lkml.kernel.org/r/20250630144212.156938-2-osalvador@suse.de
Fixes: 40549ba8f8 ("hugetlb: use new vma_lock for pmd sharing synchronization")
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Reported-by: Gavin Guo <gavinguo@igalia.com>
Closes: https://lore.kernel.org/lkml/20250513093448.592150-1-gavinguo@igalia.com/
Suggested-by: Peter Xu <peterx@redhat.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
When we try to allocate a folio via alloc_hugetlb_folio_reserve(), we need
to ensure that there is an active reservation associated with the
allocation. Otherwise, our allocation request would fail if there are no
active reservations made at that moment against any other allocations.
This is because alloc_hugetlb_folio_reserve() checks h->resv_huge_pages
before proceeding with the allocation.
Therefore, to address this issue, we just need to make a reservation (by
calling hugetlb_reserve_pages()) before we try to allocate the folio.
This will also ensure that proper region/subpool accounting is done
associated with our allocation.
Link: https://lkml.kernel.org/r/20250618053415.1036185-3-vivek.kasireddy@intel.com
Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
Cc: Steve Sistare <steven.sistare@oracle.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: David Hildenbrand <david@redhat.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "mm/memfd: Reserve hugetlb folios before allocation", v4.
There are cases when we try to pin a folio but discover that it has not
been faulted-in. So, we try to allocate it in memfd_alloc_folio() but the
allocation request may not succeed if there are no active reservations in
the system at that instant.
Therefore, making a reservation (by calling hugetlb_reserve_pages())
associated with the allocation will ensure that our request would not fail
due to lack of reservations. This will also ensure that proper
region/subpool accounting is done with our allocation.
This patch (of 3):
Currently, hugetlb_reserve_pages() returns a bool to indicate whether the
reservation map update for the range [from, to] was successful or not.
This is not sufficient for the case where the caller needs to determine
how many entries were updated for the range.
Therefore, have hugetlb_reserve_pages() return the number of entries
updated in the reservation map associated with the range [from, to].
Also, update the callers of hugetlb_reserve_pages() to handle the new
return value.
Link: https://lkml.kernel.org/r/20250618053415.1036185-1-vivek.kasireddy@intel.com
Link: https://lkml.kernel.org/r/20250618053415.1036185-2-vivek.kasireddy@intel.com
Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
Cc: Steve Sistare <steven.sistare@oracle.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: David Hildenbrand <david@redhat.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The core kernel code is currently very inconsistent in its use of
vm_flags_t vs. unsigned long. This prevents us from changing the type of
vm_flags_t in the future and is simply not correct, so correct this.
While this results in rather a lot of churn, it is a critical
pre-requisite for a future planned change to VMA flag type.
Additionally, update VMA userland tests to account for the changes.
To make review easier and to break things into smaller parts, driver and
architecture-specific changes is left for a subsequent commit.
The code has been adjusted to cascade the changes across all calling code
as far as is needed.
We will adjust architecture-specific and driver code in a subsequent patch.
Overall, this patch does not introduce any functional change.
Link: https://lkml.kernel.org/r/d1588e7bb96d1ea3fe7b9df2c699d5b4592d901d.1750274467.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Acked-by: Kees Cook <kees@kernel.org>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Acked-by: Jan Kara <jack@suse.cz>
Acked-by: Christian Brauner <brauner@kernel.org>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Acked-by: Zi Yan <ziy@nvidia.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Jann Horn <jannh@google.com>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
There are cases when we try to pin a folio but discover that it has not
been faulted-in. So, we try to allocate it in memfd_alloc_folio() but
there is a chance that we might encounter a fatal crash/failure
(VM_BUG_ON(!h->resv_huge_pages) in alloc_hugetlb_folio_reserve()) if there
are no active reservations at that instant. This issue was reported by
syzbot:
kernel BUG at mm/hugetlb.c:2403!
Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 5315 Comm: syz.0.0 Not tainted
6.13.0-rc5-syzkaller-00161-g63676eefb7a0 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS
1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:alloc_hugetlb_folio_reserve+0xbc/0xc0 mm/hugetlb.c:2403
Code: 1f eb 05 e8 56 18 a0 ff 48 c7 c7 40 56 61 8e e8 ba 21 cc 09 4c 89
f0 5b 41 5c 41 5e 41 5f 5d c3 cc cc cc cc e8 35 18 a0 ff 90 <0f> 0b 66
90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f
RSP: 0018:ffffc9000d3d77f8 EFLAGS: 00010087
RAX: ffffffff81ff6beb RBX: 0000000000000000 RCX: 0000000000100000
RDX: ffffc9000e51a000 RSI: 00000000000003ec RDI: 00000000000003ed
RBP: 1ffffffff34810d9 R08: ffffffff81ff6ba3 R09: 1ffffd4000093005
R10: dffffc0000000000 R11: fffff94000093006 R12: dffffc0000000000
R13: dffffc0000000000 R14: ffffea0000498000 R15: ffffffff9a4086c8
FS: 00007f77ac12e6c0(0000) GS:ffff88801fc00000(0000)
knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f77ab54b170 CR3: 0000000040b70000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
memfd_alloc_folio+0x1bd/0x370 mm/memfd.c:88
memfd_pin_folios+0xf10/0x1570 mm/gup.c:3750
udmabuf_pin_folios drivers/dma-buf/udmabuf.c:346 [inline]
udmabuf_create+0x70e/0x10c0 drivers/dma-buf/udmabuf.c:443
udmabuf_ioctl_create drivers/dma-buf/udmabuf.c:495 [inline]
udmabuf_ioctl+0x301/0x4e0 drivers/dma-buf/udmabuf.c:526
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:906 [inline]
__se_sys_ioctl+0xf5/0x170 fs/ioctl.c:892
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Therefore, prevent the above crash by removing the VM_BUG_ON() as there is
no need to crash the system in this situation and instead we could just
fail the allocation request.
Furthermore, as described above, the specific situation where this happens
is when we try to pin memfd folios before they are faulted-in. Although,
this is a valid thing to do, it is not the regular or the common use-case.
Let us consider the following scenarios:
1) hugetlbfs_file_mmap()
memfd_alloc_folio()
hugetlb_fault()
2) memfd_alloc_folio()
hugetlbfs_file_mmap()
hugetlb_fault()
3) hugetlbfs_file_mmap()
hugetlb_fault()
alloc_hugetlb_folio()
3) is the most common use-case where first a memfd is allocated followed
by mmap(), user writes/updates and then the relevant folios are pinned
(memfd_pin_folios()). The BUG this patch is fixing occurs in 2) because
we try to pin the folios before hugetlbfs_file_mmap() is called. So, in
this situation we try to allocate the folios before pinning them but since
we did not make any reservations, resv_huge_pages would be 0, leading to
this issue.
Link: https://lkml.kernel.org/r/20250626191116.1377761-1-vivek.kasireddy@intel.com
Fixes: 26a8ea8092 ("mm/hugetlb: fix memfd_pin_folios resv_huge_pages leak")
Reported-by: syzbot+a504cb5bae4fe117ba94@syzkaller.appspotmail.com
Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
Closes: https://syzkaller.appspot.com/bug?extid=a504cb5bae4fe117ba94
Closes: https://lore.kernel.org/all/677928b5.050a0220.3b53b0.004d.GAE@google.com/T/
Acked-by: Oscar Salvador <osalvador@suse.de>
Cc: Steve Sistare <steven.sistare@oracle.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: David Hildenbrand <david@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
In isolate_or_dissolve_huge_folio(), after acquiring the hugetlb_lock, it
is only for the purpose of obtaining the correct hstate, which is then
passed to alloc_and_dissolve_hugetlb_folio().
alloc_and_dissolve_hugetlb_folio() itself also acquires the hugetlb_lock.
We can have alloc_and_dissolve_hugetlb_folio() obtain the hstate by
itself, so that isolate_or_dissolve_huge_folio() no longer needs to
acquire the hugetlb_lock. In addition, we keep the folio_test_hugetlb()
check within isolate_or_dissolve_huge_folio(). By doing so, we can avoid
disrupting the normal path by vainly holding the hugetlb_lock.
replace_free_hugepage_folios() has the same issue, and we should address
it as well.
Addresses a possible performance problem which was added by the hotfix
113ed54ad2 ("mm/hugetlb: fix kernel NULL pointer dereference when
replacing free hugetlb folios").
Link: https://lkml.kernel.org/r/1748317010-16272-1-git-send-email-yangge1116@126.com
Fixes: 113ed54ad2 ("mm/hugetlb: fix kernel NULL pointer dereference when replacing free hugetlb folios")
Signed-off-by: Ge Yang <yangge1116@126.com>
Suggested-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Muchun Song <muchun.song@linux.dev>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <21cnbao@gmail.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Currently, __split_vma() triggers hugetlb page table unsharing through
vm_ops->may_split(). This happens before the VMA lock and rmap locks are
taken - which is too early, it allows racing VMA-locked page faults in our
process and racing rmap walks from other processes to cause page tables to
be shared again before we actually perform the split.
Fix it by explicitly calling into the hugetlb unshare logic from
__split_vma() in the same place where THP splitting also happens. At that
point, both the VMA and the rmap(s) are write-locked.
An annoying detail is that we can now call into the helper
hugetlb_unshare_pmds() from two different locking contexts:
1. from hugetlb_split(), holding:
- mmap lock (exclusively)
- VMA lock
- file rmap lock (exclusively)
2. hugetlb_unshare_all_pmds(), which I think is designed to be able to
call us with only the mmap lock held (in shared mode), but currently
only runs while holding mmap lock (exclusively) and VMA lock
Backporting note:
This commit fixes a racy protection that was introduced in commit
b30c14cd61 ("hugetlb: unshare some PMDs when splitting VMAs"); that
commit claimed to fix an issue introduced in 5.13, but it should actually
also go all the way back.
[jannh@google.com: v2]
Link: https://lkml.kernel.org/r/20250528-hugetlb-fixes-splitrace-v2-1-1329349bad1a@google.com
Link: https://lkml.kernel.org/r/20250528-hugetlb-fixes-splitrace-v2-0-1329349bad1a@google.com
Link: https://lkml.kernel.org/r/20250527-hugetlb-fixes-splitrace-v1-1-f4136f5ec58a@google.com
Fixes: 39dde65c99 ("[PATCH] shared page table for hugetlb page")
Signed-off-by: Jann Horn <jannh@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: <stable@vger.kernel.org> [b30c14cd61: hugetlb: unshare some PMDs when splitting VMAs]
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Pull more MM updates from Andrew Morton:
- "zram: support algorithm-specific parameters" from Sergey Senozhatsky
adds infrastructure for passing algorithm-specific parameters into
zram. A single parameter `winbits' is implemented at this time.
- "memcg: nmi-safe kmem charging" from Shakeel Butt makes memcg
charging nmi-safe, which is required by BFP, which can operate in NMI
context.
- "Some random fixes and cleanup to shmem" from Kemeng Shi implements
small fixes and cleanups in the shmem code.
- "Skip mm selftests instead when kernel features are not present" from
Zi Yan fixes some issues in the MM selftest code.
- "mm/damon: build-enable essential DAMON components by default" from
SeongJae Park reworks DAMON Kconfig to make it easier to enable
CONFIG_DAMON.
- "sched/numa: add statistics of numa balance task migration" from Libo
Chen adds more info into sysfs and procfs files to improve visibility
into the NUMA balancer's task migration activity.
- "selftests/mm: cow and gup_longterm cleanups" from Mark Brown
provides various updates to some of the MM selftests to make them
play better with the overall containing framework.
* tag 'mm-stable-2025-06-01-14-06' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (43 commits)
mm/khugepaged: clean up refcount check using folio_expected_ref_count()
selftests/mm: fix test result reporting in gup_longterm
selftests/mm: report unique test names for each cow test
selftests/mm: add helper for logging test start and results
selftests/mm: use standard ksft_finished() in cow and gup_longterm
selftests/damon/_damon_sysfs: skip testcases if CONFIG_DAMON_SYSFS is disabled
sched/numa: add statistics of numa balance task
sched/numa: fix task swap by skipping kernel threads
tools/testing: check correct variable in open_procmap()
tools/testing/vma: add missing function stub
mm/gup: update comment explaining why gup_fast() disables IRQs
selftests/mm: two fixes for the pfnmap test
mm/khugepaged: fix race with folio split/free using temporary reference
mm: add CONFIG_PAGE_BLOCK_ORDER to select page block order
mmu_notifiers: remove leftover stub macros
selftests/mm: deduplicate test names in madv_populate
kcov: rust: add flags for KCOV with Rust
mm: rust: make CONFIG_MMU ifdefs more narrow
mmu_gather: move tlb flush for VM_PFNMAP/VM_MIXEDMAP vmas into free_pgtables()
mm/damon/Kconfig: enable CONFIG_DAMON by default
...
Pull MM updates from Andrew Morton:
- "Add folio_mk_pte()" from Matthew Wilcox simplifies the act of
creating a pte which addresses the first page in a folio and reduces
the amount of plumbing which architecture must implement to provide
this.
- "Misc folio patches for 6.16" from Matthew Wilcox is a shower of
largely unrelated folio infrastructure changes which clean things up
and better prepare us for future work.
- "memory,x86,acpi: hotplug memory alignment advisement" from Gregory
Price adds early-init code to prevent x86 from leaving physical
memory unused when physical address regions are not aligned to memory
block size.
- "mm/compaction: allow more aggressive proactive compaction" from
Michal Clapinski provides some tuning of the (sadly, hard-coded (more
sadly, not auto-tuned)) thresholds for our invokation of proactive
compaction. In a simple test case, the reduction of a guest VM's
memory consumption was dramatic.
- "Minor cleanups and improvements to swap freeing code" from Kemeng
Shi provides some code cleaups and a small efficiency improvement to
this part of our swap handling code.
- "ptrace: introduce PTRACE_SET_SYSCALL_INFO API" from Dmitry Levin
adds the ability for a ptracer to modify syscalls arguments. At this
time we can alter only "system call information that are used by
strace system call tampering, namely, syscall number, syscall
arguments, and syscall return value.
This series should have been incorporated into mm.git's "non-MM"
branch, but I goofed.
- "fs/proc: extend the PAGEMAP_SCAN ioctl to report guard regions" from
Andrei Vagin extends the info returned by the PAGEMAP_SCAN ioctl
against /proc/pid/pagemap. This permits CRIU to more efficiently get
at the info about guard regions.
- "Fix parameter passed to page_mapcount_is_type()" from Gavin Shan
implements that fix. No runtime effect is expected because
validate_page_before_insert() happens to fix up this error.
- "kernel/events/uprobes: uprobe_write_opcode() rewrite" from David
Hildenbrand basically brings uprobe text poking into the current
decade. Remove a bunch of hand-rolled implementation in favor of
using more current facilities.
- "mm/ptdump: Drop assumption that pxd_val() is u64" from Anshuman
Khandual provides enhancements and generalizations to the pte dumping
code. This might be needed when 128-bit Page Table Descriptors are
enabled for ARM.
- "Always call constructor for kernel page tables" from Kevin Brodsky
ensures that the ctor/dtor is always called for kernel pgtables, as
it already is for user pgtables.
This permits the addition of more functionality such as "insert hooks
to protect page tables". This change does result in various
architectures performing unnecesary work, but this is fixed up where
it is anticipated to occur.
- "Rust support for mm_struct, vm_area_struct, and mmap" from Alice
Ryhl adds plumbing to permit Rust access to core MM structures.
- "fix incorrectly disallowed anonymous VMA merges" from Lorenzo
Stoakes takes advantage of some VMA merging opportunities which we've
been missing for 15 years.
- "mm/madvise: batch tlb flushes for MADV_DONTNEED and MADV_FREE" from
SeongJae Park optimizes process_madvise()'s TLB flushing.
Instead of flushing each address range in the provided iovec, we
batch the flushing across all the iovec entries. The syscall's cost
was approximately halved with a microbenchmark which was designed to
load this particular operation.
- "Track node vacancy to reduce worst case allocation counts" from
Sidhartha Kumar makes the maple tree smarter about its node
preallocation.
stress-ng mmap performance increased by single-digit percentages and
the amount of unnecessarily preallocated memory was dramaticelly
reduced.
- "mm/gup: Minor fix, cleanup and improvements" from Baoquan He removes
a few unnecessary things which Baoquan noted when reading the code.
- ""Enhance sysfs handling for memory hotplug in weighted interleave"
from Rakie Kim "enhances the weighted interleave policy in the memory
management subsystem by improving sysfs handling, fixing memory
leaks, and introducing dynamic sysfs updates for memory hotplug
support". Fixes things on error paths which we are unlikely to hit.
- "mm/damon: auto-tune DAMOS for NUMA setups including tiered memory"
from SeongJae Park introduces new DAMOS quota goal metrics which
eliminate the manual tuning which is required when utilizing DAMON
for memory tiering.
- "mm/vmalloc.c: code cleanup and improvements" from Baoquan He
provides cleanups and small efficiency improvements which Baoquan
found via code inspection.
- "vmscan: enforce mems_effective during demotion" from Gregory Price
changes reclaim to respect cpuset.mems_effective during demotion when
possible. because presently, reclaim explicitly ignores
cpuset.mems_effective when demoting, which may cause the cpuset
settings to violated.
This is useful for isolating workloads on a multi-tenant system from
certain classes of memory more consistently.
- "Clean up split_huge_pmd_locked() and remove unnecessary folio
pointers" from Gavin Guo provides minor cleanups and efficiency gains
in in the huge page splitting and migrating code.
- "Use kmem_cache for memcg alloc" from Huan Yang creates a slab cache
for `struct mem_cgroup', yielding improved memory utilization.
- "add max arg to swappiness in memory.reclaim and lru_gen" from
Zhongkun He adds a new "max" argument to the "swappiness=" argument
for memory.reclaim MGLRU's lru_gen.
This directs proactive reclaim to reclaim from only anon folios
rather than file-backed folios.
- "kexec: introduce Kexec HandOver (KHO)" from Mike Rapoport is the
first step on the path to permitting the kernel to maintain existing
VMs while replacing the host kernel via file-based kexec. At this
time only memblock's reserve_mem is preserved.
- "mm: Introduce for_each_valid_pfn()" from David Woodhouse provides
and uses a smarter way of looping over a pfn range. By skipping
ranges of invalid pfns.
- "sched/numa: Skip VMA scanning on memory pinned to one NUMA node via
cpuset.mems" from Libo Chen removes a lot of pointless VMA scanning
when a task is pinned a single NUMA mode.
Dramatic performance benefits were seen in some real world cases.
- "JFS: Implement migrate_folio for jfs_metapage_aops" from Shivank
Garg addresses a warning which occurs during memory compaction when
using JFS.
- "move all VMA allocation, freeing and duplication logic to mm" from
Lorenzo Stoakes moves some VMA code from kernel/fork.c into the more
appropriate mm/vma.c.
- "mm, swap: clean up swap cache mapping helper" from Kairui Song
provides code consolidation and cleanups related to the folio_index()
function.
- "mm/gup: Cleanup memfd_pin_folios()" from Vishal Moola does that.
- "memcg: Fix test_memcg_min/low test failures" from Waiman Long
addresses some bogus failures which are being reported by the
test_memcontrol selftest.
- "eliminate mmap() retry merge, add .mmap_prepare hook" from Lorenzo
Stoakes commences the deprecation of file_operations.mmap() in favor
of the new file_operations.mmap_prepare().
The latter is more restrictive and prevents drivers from messing with
things in ways which, amongst other problems, may defeat VMA merging.
- "memcg: decouple memcg and objcg stocks"" from Shakeel Butt decouples
the per-cpu memcg charge cache from the objcg's one.
This is a step along the way to making memcg and objcg charging
NMI-safe, which is a BPF requirement.
- "mm/damon: minor fixups and improvements for code, tests, and
documents" from SeongJae Park is yet another batch of miscellaneous
DAMON changes. Fix and improve minor problems in code, tests and
documents.
- "memcg: make memcg stats irq safe" from Shakeel Butt converts memcg
stats to be irq safe. Another step along the way to making memcg
charging and stats updates NMI-safe, a BPF requirement.
- "Let unmap_hugepage_range() and several related functions take folio
instead of page" from Fan Ni provides folio conversions in the
hugetlb code.
* tag 'mm-stable-2025-05-31-14-50' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (285 commits)
mm: pcp: increase pcp->free_count threshold to trigger free_high
mm/hugetlb: convert use of struct page to folio in __unmap_hugepage_range()
mm/hugetlb: refactor __unmap_hugepage_range() to take folio instead of page
mm/hugetlb: refactor unmap_hugepage_range() to take folio instead of page
mm/hugetlb: pass folio instead of page to unmap_ref_private()
memcg: objcg stock trylock without irq disabling
memcg: no stock lock for cpu hot-unplug
memcg: make __mod_memcg_lruvec_state re-entrant safe against irqs
memcg: make count_memcg_events re-entrant safe against irqs
memcg: make mod_memcg_state re-entrant safe against irqs
memcg: move preempt disable to callers of memcg_rstat_updated
memcg: memcg_rstat_updated re-entrant safe against irqs
mm: khugepaged: decouple SHMEM and file folios' collapse
selftests/eventfd: correct test name and improve messages
alloc_tag: check mem_profiling_support in alloc_tag_init
Docs/damon: update titles and brief introductions to explain DAMOS
selftests/damon/_damon_sysfs: read tried regions directories in order
mm/damon/tests/core-kunit: add a test for damos_set_filters_default_reject()
mm/damon/paddr: remove unused variable, folio_list, in damon_pa_stat()
mm/damon/sysfs-schemes: fix wrong comment on damons_sysfs_quota_goal_metric_strs
...
If, during a mremap() operation for a hugetlb-backed memory mapping,
copy_vma() fails after the source vma has been duplicated and opened (ie.
vma_link() fails), the error is handled by closing the new vma. This
updates the hugetlbfs reservation counter of the reservation map which at
this point is referenced by both the source vma and the new copy. As a
result, once the new vma has been freed and copy_vma() returns, the
reservation counter for the source vma will be incorrect.
This patch addresses this corner case by clearing the hugetlb private page
reservation reference for the new vma and decrementing the reference
before closing the vma, so that vma_close() won't update the reservation
counter. This is also what copy_vma_and_data() does with the source vma
if copy_vma() succeeds, so a helper function has been added to do the
fixup in both functions.
The issue was reported by a private syzbot instance and can be reproduced
using the C reproducer in [1]. It's also a possible duplicate of public
syzbot report [2]. The WARNING report is:
============================================================
page_counter underflow: -1024 nr_pages=1024
WARNING: CPU: 0 PID: 3287 at mm/page_counter.c:61 page_counter_cancel+0xf6/0x120
Modules linked in:
CPU: 0 UID: 0 PID: 3287 Comm: repro__WARNING_ Not tainted 6.15.0-rc7+ #54 NONE
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.3-2-gc13ff2cd-prebuilt.qemu.org 04/01/2014
RIP: 0010:page_counter_cancel+0xf6/0x120
Code: ff 5b 41 5e 41 5f 5d c3 cc cc cc cc e8 f3 4f 8f ff c6 05 64 01 27 06 01 48 c7 c7 60 15 f8 85 48 89 de 4c 89 fa e8 2a a7 51 ff <0f> 0b e9 66 ff ff ff 44 89 f9 80 e1 07 38 c1 7c 9d 4c 81
RSP: 0018:ffffc900025df6a0 EFLAGS: 00010246
RAX: 2edfc409ebb44e00 RBX: fffffffffffffc00 RCX: ffff8880155f0000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: dffffc0000000000 R08: ffffffff81c4a23c R09: 1ffff1100330482a
R10: dffffc0000000000 R11: ffffed100330482b R12: 0000000000000000
R13: ffff888058a882c0 R14: ffff888058a882c0 R15: 0000000000000400
FS: 0000000000000000(0000) GS:ffff88808fc53000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000004b33e0 CR3: 00000000076d6000 CR4: 00000000000006f0
Call Trace:
<TASK>
page_counter_uncharge+0x33/0x80
hugetlb_cgroup_uncharge_counter+0xcb/0x120
hugetlb_vm_op_close+0x579/0x960
? __pfx_hugetlb_vm_op_close+0x10/0x10
remove_vma+0x88/0x130
exit_mmap+0x71e/0xe00
? __pfx_exit_mmap+0x10/0x10
? __mutex_unlock_slowpath+0x22e/0x7f0
? __pfx_exit_aio+0x10/0x10
? __up_read+0x256/0x690
? uprobe_clear_state+0x274/0x290
? mm_update_next_owner+0xa9/0x810
__mmput+0xc9/0x370
exit_mm+0x203/0x2f0
? __pfx_exit_mm+0x10/0x10
? taskstats_exit+0x32b/0xa60
do_exit+0x921/0x2740
? do_raw_spin_lock+0x155/0x3b0
? __pfx_do_exit+0x10/0x10
? __pfx_do_raw_spin_lock+0x10/0x10
? _raw_spin_lock_irq+0xc5/0x100
do_group_exit+0x20c/0x2c0
get_signal+0x168c/0x1720
? __pfx_get_signal+0x10/0x10
? schedule+0x165/0x360
arch_do_signal_or_restart+0x8e/0x7d0
? __pfx_arch_do_signal_or_restart+0x10/0x10
? __pfx___se_sys_futex+0x10/0x10
syscall_exit_to_user_mode+0xb8/0x2c0
do_syscall_64+0x75/0x120
entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x422dcd
Code: Unable to access opcode bytes at 0x422da3.
RSP: 002b:00007ff266cdb208 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: 0000000000000001 RBX: 00007ff266cdbcdc RCX: 0000000000422dcd
RDX: 00000000000f4240 RSI: 0000000000000081 RDI: 00000000004c7bec
RBP: 00007ff266cdb220 R08: 203a6362696c6720 R09: 203a6362696c6720
R10: 0000200000c00000 R11: 0000000000000246 R12: ffffffffffffffd0
R13: 0000000000000002 R14: 00007ffe1cb5f520 R15: 00007ff266cbb000
</TASK>
============================================================
Link: https://lkml.kernel.org/r/20250523-warning_in_page_counter_cancel-v2-1-b6df1a8cfefd@igalia.com
Link: https://people.igalia.com/rcn/kernel_logs/20250422__WARNING_in_page_counter_cancel__repro.c [1]
Link: https://lore.kernel.org/all/67000a50.050a0220.49194.048d.GAE@google.com/ [2]
Signed-off-by: Ricardo Cañuelo Navarro <rcn@igalia.com>
Suggested-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Florent Revest <revest@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Hugetlb boot allocation has used online nodes for allocation since commit
de55996d71 ("mm/hugetlb: use online nodes for bootmem allocation").
This was needed to be able to do the allocations earlier in boot, before
N_MEMORY was set.
This might lead to a different distribution of gigantic hugepages across
NUMA nodes if there are memoryless nodes in the system.
What happens is that the memoryless nodes are tried, but then the memblock
allocation fails and falls back, which usually means that the node that
has the highest physical address available will be used (top-down
allocation). While this will end up getting the same number of hugetlb
pages, they might not be be distributed the same way. The fallback for
each memoryless node might not end up coming from the same node as the
successful round-robin allocation from N_MEMORY nodes.
While administrators that rely on having a specific number of hugepages
per node should use the hugepages=N:X syntax, it's better not to change
the old behavior for the plain hugepages=N case.
To do this, construct a nodemask for hugetlb bootmem purposes only,
containing nodes that have memory. Then use that for round-robin bootmem
allocations.
This saves some cycles, and the added advantage here is that hugetlb_cma
can use it too, avoiding the older issue of pointless attempts to create a
CMA area for memoryless nodes (which will also cause the per-node CMA area
size to be too small).
Link: https://lkml.kernel.org/r/20250402205613.3086864-1-fvdl@google.com
Fixes: de55996d71 ("mm/hugetlb: use online nodes for bootmem allocation")
Signed-off-by: Frank van der Linden <fvdl@google.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Luiz Capitulino <luizcap@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Before trying to allocate a page, gather_surplus_pages() sets up a
nodemask for the nodes we can allocate from, but instead of passing the
nodemask down the road to the page allocator, it iterates over the nodes
within that nodemask right there, meaning that the page allocator will
receive a preferred_nid and a null nodemask.
This is a problem when using a memory policy, because it might be that the
page allocator ends up using a node as a fallback which is not represented
in the policy.
Avoid that by passing the nodemask directly to the page allocator, so it
can filter out fallback nodes that are not part of the nodemask.
Link: https://lkml.kernel.org/r/20250415121503.376811-1-osalvador@suse.de
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: David Hildenbrand <david@redhat.com>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
During our testing with hugetlb subpool enabled, we observe that
hstate->resv_huge_pages may underflow into negative values. Root cause
analysis reveals a race condition in subpool reservation fallback handling
as follow:
hugetlb_reserve_pages()
/* Attempt subpool reservation */
gbl_reserve = hugepage_subpool_get_pages(spool, chg);
/* Global reservation may fail after subpool allocation */
if (hugetlb_acct_memory(h, gbl_reserve) < 0)
goto out_put_pages;
out_put_pages:
/* This incorrectly restores reservation to subpool */
hugepage_subpool_put_pages(spool, chg);
When hugetlb_acct_memory() fails after subpool allocation, the current
implementation over-commits subpool reservations by returning the full
'chg' value instead of the actual allocated 'gbl_reserve' amount. This
discrepancy propagates to global reservations during subsequent releases,
eventually causing resv_huge_pages underflow.
This problem can be trigger easily with the following steps:
1. reverse hugepage for hugeltb allocation
2. mount hugetlbfs with min_size to enable hugetlb subpool
3. alloc hugepages with two task(make sure the second will fail due to
insufficient amount of hugepages)
4. with for a few seconds and repeat step 3 which will make
hstate->resv_huge_pages to go below zero.
To fix this problem, return corrent amount of pages to subpool during the
fallback after hugepage_subpool_get_pages is called.
Link: https://lkml.kernel.org/r/20250410062633.3102457-1-mawupeng1@huawei.com
Fixes: 1c5ecae3a9 ("hugetlbfs: add minimum size accounting to subpools")
Signed-off-by: Wupeng Ma <mawupeng1@huawei.com>
Tested-by: Joshua Hahn <joshua.hahnjy@gmail.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: Ma Wupeng <mawupeng1@huawei.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Since commit d2d7867140 ("mm/hugetlb: enable bootmem allocation from CMA
areas"), a flag is used to mark hugetlb folios as allocated from CMA.
This flag is also used to decide if it should be freed to CMA.
However, the flag isn't copied to the smaller folios when a hugetlb folio
is broken up for demotion, which would cause it to be freed incorrectly.
Fix this by copying the flag to the smaller order hugetlb pages created
from the original one.
Link: https://lkml.kernel.org/r/20250501044325.20365-1-fvdl@google.com
Fixes: d2d7867140 ("mm/hugetlb: enable bootmem allocation from CMA areas")
Signed-off-by: Frank van der Linden <fvdl@google.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Jane Chu <Jane.Chu@oracle.com>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
In set_max_huge_pages(), min_count is computed taking into account surplus
huge pages, which might lead in some cases to not be able to free huge
pages and end up accounting them as surplus instead.
One way to solve it is to subtract surplus_huge_pages directly, but we
cannot do it blindly because there might be surplus pages that are also
free pages, which might happen when we fail to restore the vmemmap for
optimized hvo pages. So we could be subtracting the same page twice.
In order to work this around, let us first compute the number of free
persistent pages, and use that along with surplus pages to compute
min_count.
Steps to reproduce:
1) create 5 hugetlb folios in Node0
2) run a program to use all the hugetlb folios
3) echo 0 > nr_hugepages for Node0 to free the hugetlb folios. Thus
the 5 hugetlb folios in Node0 are accounted as surplus.
4) create 5 hugetlb folios in Node1
5) echo 0 > nr_hugepages for Node1 to free the hugetlb folios
The result:
Node0 Node1
Total 5 5
Free 0 5
Surp 5 5
The result with this patch:
Node0 Node1
Total 5 0
Free 0 0
Surp 5 0
Link: https://lkml.kernel.org/r/20250409055957.3774471-1-tujinjiang@huawei.com
Link: https://lkml.kernel.org/r/20250407124706.2688092-1-tujinjiang@huawei.com
Fixes: 9a30523066 ("hugetlb: add per node hstate attributes")
Signed-off-by: Jinjiang Tu <tujinjiang@huawei.com>
Acked-by: Oscar Salvador <osalvador@suse.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
In alloc_surplus_hugetlb_folio(), we increase nr_huge_pages and
surplus_huge_pages separately. In the middle window, if we set
nr_hugepages to smaller and satisfy count < persistent_huge_pages(h), the
surplus_huge_pages will be increased by adjust_pool_surplus().
After adding delay in the middle window, we can reproduce the problem
easily by following step:
1. echo 3 > /proc/sys/vm/nr_overcommit_hugepages
2. mmap two hugepages. When nr_huge_pages=2 and surplus_huge_pages=1,
goto step 3.
3. echo 0 > /proc/sys/vm/nr_huge_pages
Finally, nr_huge_pages is less than surplus_huge_pages.
To fix the problem, call only_alloc_fresh_hugetlb_folio() instead and
move down __prep_account_new_huge_page() into the hugetlb_lock.
Link: https://lkml.kernel.org/r/20250305035409.2391344-1-liushixin2@huawei.com
Fixes: 0c397daea1 ("mm, hugetlb: further simplify hugetlb allocation API")
Signed-off-by: Liu Shixin <liushixin2@huawei.com>
Acked-by: Peter Xu <peterx@redhat.com>
Acked-by: Oscar Salvador <osalvador@suse.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Liu Shixin <liushixin2@huawei.com>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "Add a command line option that enables control of how many
threads should be used to allocate huge pages", v2.
Allocating huge pages can take a very long time on servers with terabytes
of memory even when they are allocated at boot time where the allocation
happens in parallel.
Before this series, the kernel used a hard coded value of 2 threads per
NUMA node for these allocations. This value might have been good enough
in the past but it is not sufficient to fully utilize newer systems.
This series changes the default so the kernel uses 25% of the available
hardware threads for these allocations. In addition, we allow the user
that wish to micro-optimize the allocation time to override this value via
a new kernel parameter.
We tested this on 2 generations of Xeon CPUs and the results show a big
improvement of the overall allocation time.
+-----------------------+-------+-------+-------+-------+-------+
| threads | 8 | 16 | 32 | 64 | 128 |
+-----------------------+-------+-------+-------+-------+-------+
| skylake 144 cpus | 44s | 22s | 16s | 19s | 20s |
| cascade lake 192 cpus | 39s | 20s | 11s | 10s | 9s |
+-----------------------+-------+-------+-------+-------+-------+
On skylake, we see an improvment of 2.75x when using 32 threads, on
cascade lake we can get even better at 4.3x when we use 128 threads.
This speedup is quite significant and users of large machines like these
should have the option to make the machines boot as fast as possible.
This patch (of 3):
Before this patch, the kernel currently used a hard coded value of 2
threads per NUMA node for these allocations.
This patch changes this policy and the kernel now uses 25% of the
available hardware threads for the allocations.
Link: https://lkml.kernel.org/r/20250227-hugepage-parameter-v2-0-7db8c6dc0453@cyberus-technology.de
Link: https://lkml.kernel.org/r/20250227-hugepage-parameter-v2-1-7db8c6dc0453@cyberus-technology.de
Signed-off-by: Thomas Prescher <thomas.prescher@cyberus-technology.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
For large systems, the overhead of vmemmap pages for hugetlb is
substantial. It's about 1.5% of memory, which is about 45G for a 3T
system. If you want to configure most of that system for hugetlb (e.g.
to use as backing memory for VMs), there is a chance of running out of
memory on boot, even though you know that the 45G will become available
later.
To avoid this scenario, and since it's a waste to first allocate and then
free that 45G during boot, do pre-HVO for hugetlb bootmem allocated pages
('gigantic' pages).
pre-HVO is done by adding functions that are called from
sparse_init_nid_early and sparse_init_nid_late. The first is called
before memmap allocation, so it takes care of allocating memmap HVO-style.
The second verifies that all bootmem pages look good, specifically it
checks that they do not intersect with multiple zones. This can only be
done from sparse_init_nid_late path, when zones have been initialized.
The hugetlb page size must be aligned to the section size, and aligned to
the size of memory described by the number of page structures contained in
one PMD (since pre-HVO is not prepared to split PMDs). This should be
true for most 'gigantic' pages, it is for 1G pages on x86, where both of
these alignment requirements are 128M.
This will only have an effect if hugetlb_bootmem_alloc was called early in
boot. If not, it won't do anything, and HVO for bootmem hugetlb pages
works as before.
Link: https://lkml.kernel.org/r/20250228182928.2645936-20-fvdl@google.com
Signed-off-by: Frank van der Linden <fvdl@google.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dan Carpenter <dan.carpenter@linaro.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Joao Martins <joao.m.martins@oracle.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roman Gushchin (Cruise) <roman.gushchin@linux.dev>
Cc: Usama Arif <usamaarif642@gmail.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
