It is possible for a bulk operation (MA_STATE_BULK is set) to enter the
new_end < mt_min_slots[type] case and set wr_rebalance as a store type.
This is incorrect as bulk stores do not rebalance per write, but rather
after the all of the writes are done through the mas_bulk_rebalance()
path. Therefore, add a check to make sure MA_STATE_BULK is not set before
we return wr_rebalance as the store type.
Also add a test to make sure wr_rebalance is never the store type when
doing bulk operations via mas_expected_entries()
This is a hotfix for this rc however it has no userspace effects as there
are no users of the bulk insertion mode.
Link: https://lkml.kernel.org/r/20241011214451.7286-1-sidhartha.kumar@oracle.com
Fixes: 5d659bbb52 ("maple_tree: introduce mas_wr_store_type()")
Suggested-by: Liam Howlett <liam.howlett@oracle.com>
Signed-off-by: Sidhartha <sidhartha.kumar@oracle.com>
Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Liam Howlett <liam.howlett@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Pull memblock updates from Mike Rapoport:
- new memblock_estimated_nr_free_pages() helper to replace
totalram_pages() which is less accurate when
CONFIG_DEFERRED_STRUCT_PAGE_INIT is set
- fixes for memblock tests
* tag 'memblock-v6.12-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rppt/memblock:
s390/mm: get estimated free pages by memblock api
kernel/fork.c: get estimated free pages by memblock api
mm/memblock: introduce a new helper memblock_estimated_nr_free_pages()
memblock test: fix implicit declaration of function 'strscpy'
memblock test: fix implicit declaration of function 'isspace'
memblock test: fix implicit declaration of function 'memparse'
memblock test: add the definition of __setup()
memblock test: fix implicit declaration of function 'virt_to_phys'
tools/testing: abstract two init.h into common include directory
memblock tests: include export.h in linkage.h as kernel dose
memblock tests: include memory_hotplug.h in mmzone.h as kernel dose
Introduce mas_wr_store_type() which will set the correct store type based
on a walk of the tree. In mas_wr_node_store() the <= min_slots condition
is changed to < as if new_end is = to mt_min_slots then there is not
enough room.
mas_prealloc_calc() is also introduced to abstract the calculation used to
determine the number of nodes needed for a store operation.
In this change a call to mas_reset() is removed in the error case of
mas_prealloc(). This is only needed in the MA_STATE_REBALANCE case of
mas_destroy(). We can move the call to mas_reset() directly to
mas_destroy().
Also, add a test case to validate the order that we check the store type
in is correct. This test models a vma expanding and then shrinking which
is part of the boot process.
Link: https://lkml.kernel.org/r/20240814161944.55347-5-sidhartha.kumar@oracle.com
Signed-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
mas_preallocate() defaults to requesting 1 node for preallocation and then
,depending on the type of store, will update the request variable. There
isn't a check for a slot store type, so slot stores are preallocating the
default 1 node. Slot stores do not require any additional nodes, so add a
check for the slot store case that will bypass node_count_gfp(). Update
the tests to reflect that slot stores do not require allocations.
User visible effects of this bug include increased memory usage from the
unneeded node that was allocated.
Link: https://lkml.kernel.org/r/20231213205058.386589-1-sidhartha.kumar@oracle.com
Fixes: 0b8bb544b1 ("maple_tree: update mas_preallocate() testing")
Signed-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Peng Zhang <zhangpeng.00@bytedance.com>
Cc: <stable@vger.kernel.org> [6.6+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
During the development of the maple tree, the strategy of freeing multiple
nodes changed and, in the process, the pivots were reused to store
pointers to dead nodes. To ensure the readers see accurate pivots, the
writers need to mark the nodes as dead and call smp_wmb() to ensure any
readers can identify the node as dead before using the pivot values.
There were two places where the old method of marking the node as dead
without smp_wmb() were being used, which resulted in RCU readers seeing
the wrong pivot value before seeing the node was dead. Fix this race
condition by using mte_set_node_dead() which has the smp_wmb() call to
ensure the race is closed.
Add a WARN_ON() to the ma_free_rcu() call to ensure all nodes being freed
are marked as dead to ensure there are no other call paths besides the two
updated paths.
This is necessary for the RCU mode of the maple tree.
Link: https://lkml.kernel.org/r/20230227173632.3292573-6-surenb@google.com
Fixes: 54a611b605 ("Maple Tree: add new data structure")
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Preallocations are common in the VMA code to avoid allocating under
certain locking conditions. The preallocations must also cover the
worst-case scenario. Removing the GFP_ZERO flag from the
kmem_cache_alloc() (and bulk variant) calls will reduce the amount of time
spent zeroing memory that may not be used. Only zero out the necessary
area to keep track of the allocations in the maple state. Zero the entire
node prior to using it in the tree.
This required internal changes to node counting on allocation, so the test
code is also updated.
This restores some micro-benchmark performance: up to +9% in mmtests mmap1
by my testing +10% to +20% in mmap, mmapaddr, mmapmany tests reported by
Red Hat
Link: https://bugzilla.redhat.com/show_bug.cgi?id=2149636
Link: https://lkml.kernel.org/r/20230105160427.2988454-1-Liam.Howlett@oracle.com
Signed-off-by: Liam Howlett <Liam.Howlett@oracle.com>
Reported-by: Jirka Hladky <jhladky@redhat.com>
Suggested-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Along the development cycle, the testing code support for module/in-kernel
compiles was removed. Restore this functionality by moving any internal
API tests to the userspace side, as well as threading tests. Fix the
lockdep issues and add a way to reduce memory usage so the tests can
complete with KASAN + memleak detection. Make the tests work on 32 bit
hosts where possible and detect 32 bit hosts in the radix test suite.
[akpm@linux-foundation.org: fix module export]
[akpm@linux-foundation.org: fix it some more]
[liam.howlett@oracle.com: fix compile warnings on 32bit build in check_find()]
Link: https://lkml.kernel.org/r/20221107203816.1260327-1-Liam.Howlett@oracle.com
Link: https://lkml.kernel.org/r/20221028180415.3074673-1-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "Introducing the Maple Tree"
The maple tree is an RCU-safe range based B-tree designed to use modern
processor cache efficiently. There are a number of places in the kernel
that a non-overlapping range-based tree would be beneficial, especially
one with a simple interface. If you use an rbtree with other data
structures to improve performance or an interval tree to track
non-overlapping ranges, then this is for you.
The tree has a branching factor of 10 for non-leaf nodes and 16 for leaf
nodes. With the increased branching factor, it is significantly shorter
than the rbtree so it has fewer cache misses. The removal of the linked
list between subsequent entries also reduces the cache misses and the need
to pull in the previous and next VMA during many tree alterations.
The first user that is covered in this patch set is the vm_area_struct,
where three data structures are replaced by the maple tree: the augmented
rbtree, the vma cache, and the linked list of VMAs in the mm_struct. The
long term goal is to reduce or remove the mmap_lock contention.
The plan is to get to the point where we use the maple tree in RCU mode.
Readers will not block for writers. A single write operation will be
allowed at a time. A reader re-walks if stale data is encountered. VMAs
would be RCU enabled and this mode would be entered once multiple tasks
are using the mm_struct.
Davidlor said
: Yes I like the maple tree, and at this stage I don't think we can ask for
: more from this series wrt the MM - albeit there seems to still be some
: folks reporting breakage. Fundamentally I see Liam's work to (re)move
: complexity out of the MM (not to say that the actual maple tree is not
: complex) by consolidating the three complimentary data structures very
: much worth it considering performance does not take a hit. This was very
: much a turn off with the range locking approach, which worst case scenario
: incurred in prohibitive overhead. Also as Liam and Matthew have
: mentioned, RCU opens up a lot of nice performance opportunities, and in
: addition academia[1] has shown outstanding scalability of address spaces
: with the foundation of replacing the locked rbtree with RCU aware trees.
A similar work has been discovered in the academic press
https://pdos.csail.mit.edu/papers/rcuvm:asplos12.pdf
Sheer coincidence. We designed our tree with the intention of solving the
hardest problem first. Upon settling on a b-tree variant and a rough
outline, we researched ranged based b-trees and RCU b-trees and did find
that article. So it was nice to find reassurances that we were on the
right path, but our design choice of using ranges made that paper unusable
for us.
This patch (of 70):
The maple tree is an RCU-safe range based B-tree designed to use modern
processor cache efficiently. There are a number of places in the kernel
that a non-overlapping range-based tree would be beneficial, especially
one with a simple interface. If you use an rbtree with other data
structures to improve performance or an interval tree to track
non-overlapping ranges, then this is for you.
The tree has a branching factor of 10 for non-leaf nodes and 16 for leaf
nodes. With the increased branching factor, it is significantly shorter
than the rbtree so it has fewer cache misses. The removal of the linked
list between subsequent entries also reduces the cache misses and the need
to pull in the previous and next VMA during many tree alterations.
The first user that is covered in this patch set is the vm_area_struct,
where three data structures are replaced by the maple tree: the augmented
rbtree, the vma cache, and the linked list of VMAs in the mm_struct. The
long term goal is to reduce or remove the mmap_lock contention.
The plan is to get to the point where we use the maple tree in RCU mode.
Readers will not block for writers. A single write operation will be
allowed at a time. A reader re-walks if stale data is encountered. VMAs
would be RCU enabled and this mode would be entered once multiple tasks
are using the mm_struct.
There is additional BUG_ON() calls added within the tree, most of which
are in debug code. These will be replaced with a WARN_ON() call in the
future. There is also additional BUG_ON() calls within the code which
will also be reduced in number at a later date. These exist to catch
things such as out-of-range accesses which would crash anyways.
Link: https://lkml.kernel.org/r/20220906194824.2110408-1-Liam.Howlett@oracle.com
Link: https://lkml.kernel.org/r/20220906194824.2110408-2-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Tested-by: David Howells <dhowells@redhat.com>
Tested-by: Sven Schnelle <svens@linux.ibm.com>
Tested-by: Yu Zhao <yuzhao@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: David Hildenbrand <david@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
