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authorSeongJae Park <sj@kernel.org>2024-08-26 06:23:20 +0200
committerAndrew Morton <akpm@linux-foundation.org>2024-09-10 01:38:59 +0200
commitb7315fbb64736acad3cd33851884b222b00dc0f4 (patch)
tree3101d6d2f04c97c21390dfea6a82a226d3296751
parentmm: remove putback_lru_page() (diff)
downloadlinux-b7315fbb64736acad3cd33851884b222b00dc0f4.tar.xz
linux-b7315fbb64736acad3cd33851884b222b00dc0f4.zip
mm/damon/core: introduce per-context region priorities histogram buffer
Patch series "replace per-quota region priorities histogram buffer with per-context one". Each DAMOS quota (struct damos_quota) maintains a histogram for total regions size per its prioritization score. DAMOS calcultes minimum prioritization score of regions that are ok to apply the DAMOS action to while respecting the quota. The histogram is constructed only for the calculation of the minimum score in damos_adjust_quota() for each quota which called by kdamond_fn(). Hence, there is no real reason to have per-quota histogram. Only per-kdamond histogram is needed, since parallel kdamonds could have races otherwise. The current implementation is only wasting the memory, and can easily cause unintended stack usage[1]. So, introducing a per-kdamond histogram and replacing the per-quota one with it would be the right solution for the issue. However, supporting multiple DAMON contexts per kdamond is still an ongoing work[2] without a clear estimated time of arrival. Meanwhile, per-context histogram could be an effective and straightforward solution having no blocker. Let's fix the problem first in the way. This patch (of 4): Introduce per-context buffer for region priority scores-total size histogram. Same to the per-quota one (->histogram of struct damos_quota), the new buffer is hidden from DAMON API users by being defined as a private field of DAMON context structure. It is dynamically allocated and de-allocated at the beginning and ending of the execution of the kdamond by kdamond_fn() itself. [1] commit 0742cadf5e4c ("mm/damon/lru_sort: adjust local variable to dynamic allocation") [2] https://lore.kernel.org/20240531122320.909060-1-yorha.op@gmail.com Link: https://lkml.kernel.org/r/20240826042323.87025-1-sj@kernel.org Link: https://lkml.kernel.org/r/20240826042323.87025-2-sj@kernel.org Signed-off-by: SeongJae Park <sj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
-rw-r--r--include/linux/damon.h2
-rw-r--r--mm/damon/core.c5
2 files changed, 7 insertions, 0 deletions
diff --git a/include/linux/damon.h b/include/linux/damon.h
index 27c546bfc6d4..60cb8eada3d6 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -630,6 +630,8 @@ struct damon_ctx {
unsigned long next_ops_update_sis;
/* for waiting until the execution of the kdamond_fn is started */
struct completion kdamond_started;
+ /* for scheme quotas prioritization */
+ unsigned long *regions_score_histogram;
/* public: */
struct task_struct *kdamond;
diff --git a/mm/damon/core.c b/mm/damon/core.c
index 086294279b07..40266d85eebf 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -1957,6 +1957,10 @@ static int kdamond_fn(void *data)
ctx->ops.init(ctx);
if (ctx->callback.before_start && ctx->callback.before_start(ctx))
goto done;
+ ctx->regions_score_histogram = kmalloc_array(DAMOS_MAX_SCORE + 1,
+ sizeof(*ctx->regions_score_histogram), GFP_KERNEL);
+ if (!ctx->regions_score_histogram)
+ goto done;
sz_limit = damon_region_sz_limit(ctx);
@@ -2034,6 +2038,7 @@ done:
ctx->callback.before_terminate(ctx);
if (ctx->ops.cleanup)
ctx->ops.cleanup(ctx);
+ kfree(ctx->regions_score_histogram);
pr_debug("kdamond (%d) finishes\n", current->pid);
mutex_lock(&ctx->kdamond_lock);