Patch series "mm/damon: fix divide by zero and its samples", v3.
This series includes fixes against damon and its samples to make it safer
when damon sample starting fails.
It includes the following changes.
- fix unexpected divide by zero crash for zero size regions
- fix bugs for damon samples in case of start failures
This patch (of 4):
The damon_sample_prcl_start() can fail so we must reset the "enable"
parameter to "false" again for proper rollback.
In such cases, setting Y to "enable" then N triggers the following crash
because damon sample start failed but the "enable" stays as Y.
[ 2441.419649] damon_sample_prcl: start
[ 2454.146817] damon_sample_prcl: stop
[ 2454.146862] ------------[ cut here ]------------
[ 2454.146865] kernel BUG at mm/slub.c:546!
[ 2454.148183] Oops: invalid opcode: 0000 [#1] SMP NOPTI
...
[ 2454.167555] Call Trace:
[ 2454.167822] <TASK>
[ 2454.168061] damon_destroy_ctx+0x78/0x140
[ 2454.168454] damon_sample_prcl_enable_store+0x8d/0xd0
[ 2454.168932] param_attr_store+0xa1/0x120
[ 2454.169315] module_attr_store+0x20/0x50
[ 2454.169695] sysfs_kf_write+0x72/0x90
[ 2454.170065] kernfs_fop_write_iter+0x150/0x1e0
[ 2454.170491] vfs_write+0x315/0x440
[ 2454.170833] ksys_write+0x69/0xf0
[ 2454.171162] __x64_sys_write+0x19/0x30
[ 2454.171525] x64_sys_call+0x18b2/0x2700
[ 2454.171900] do_syscall_64+0x7f/0x680
[ 2454.172258] ? exit_to_user_mode_loop+0xf6/0x180
[ 2454.172694] ? clear_bhb_loop+0x30/0x80
[ 2454.173067] ? clear_bhb_loop+0x30/0x80
[ 2454.173439] entry_SYSCALL_64_after_hwframe+0x76/0x7e
Link: https://lkml.kernel.org/r/20250702000205.1921-1-honggyu.kim@sk.com
Link: https://lkml.kernel.org/r/20250702000205.1921-2-honggyu.kim@sk.com
Fixes: 2aca254620 ("samples/damon: introduce a skeleton of a smaple DAMON module for proactive reclamation")
Signed-off-by: Honggyu Kim <honggyu.kim@sk.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
DAMON is not only for monitoring of access patterns, but also for
access-aware system operations. For the system operations, DAMON provides
a feature called DAMOS (Data Access Monitoring-based Operation Schemes).
There is no sample API usage of DAMOS, though. Copy the working set size
estimation sample modules with changed names of the module and symbols, to
use it as a skeleton for a sample module showing the DAMOS API usage. The
following commit will make it proactively reclaim cold memory of the given
process, using DAMOS.
Link: https://lkml.kernel.org/r/20241210215030.85675-5-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Implement the DAMON-based working set size estimation logic. The logic
iterates memory regions in DAMON-generated access pattern snapshot for
every aggregation interval and get the total sum of the size of any region
having one or higher 'nr_accesses' count. That is, it assumes any region
having one or higher 'nr_accesses' to be a part of the working set. The
estimated value is reported to the user by printing it to the kernel log.
Link: https://lkml.kernel.org/r/20241210215030.85675-4-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Start running DAMON to monitor accesses of a process that the user
specified via 'target_pid' parameter, when 'y' is passed to 'enable'
parameter. Stop running DAMON when 'n' is passed to 'enable' parameter.
Estimating the working set size from DAMON's monitoring results and
reporting it to the user will be implemented by the following commit.
Link: https://lkml.kernel.org/r/20241210215030.85675-3-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "mm/damon: add sample modules".
Implement a proactive cold memory regions reclaiming logic of prcl sample
module using DAMOS. The logic treats memory regions that not accessed at
all for five or more seconds as cold, and reclaim those as soon as found.
This patch (of 5):
Add a skeleton for a sample DAMON static module that can be used for
estimating working set size of a given process. Note that it is a static
module since DAMON is not exporting symbols to loadable modules for now.
It exposes two module parameters, namely 'pid' and 'enable'. 'pid' will
specify the process that the module will estimate the working set size of.
'enable' will receive whether to start or stop the estimation. Because
this is just a skeleton, the parameters do nothing, though. The
functionalities will be implemented by following commits.
Link: https://lkml.kernel.org/r/20241210215030.85675-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20241210215030.85675-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
