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authorSergey Senozhatsky <senozhatsky@chromium.org>2023-04-18 10:46:39 +0300
committerAndrew Morton <akpm@linux-foundation.org>2023-04-22 00:52:04 +0300
commitd2658f2052c7db6ec0a79977205f8cf1cb9effc2 (patch)
treeaa1723db2df992b5dc3bbdbc76d9de79a2ca3091 /mm/zsmalloc.c
parent07115fcc15b4aa5c268fb80b82ad15868a82a285 (diff)
downloadlinux-d2658f2052c7db6ec0a79977205f8cf1cb9effc2.tar.xz
zsmalloc: allow only one active pool compaction context
zsmalloc pool can be compacted concurrently by many contexts, e.g. cc1 handle_mm_fault() do_anonymous_page() __alloc_pages_slowpath() try_to_free_pages() do_try_to_free_pages( lru_gen_shrink_node() shrink_slab() do_shrink_slab() zs_shrinker_scan() zs_compact() Pool compaction is currently (basically) single-threaded as it is performed under pool->lock. Having multiple compaction threads results in unnecessary contention, as each thread competes for pool->lock. This, in turn, affects all zsmalloc operations such as zs_malloc(), zs_map_object(), zs_free(), etc. Introduce the pool->compaction_in_progress atomic variable, which ensures that only one compaction context can run at a time. This reduces overall pool->lock contention in (corner) cases when many contexts attempt to shrink zspool simultaneously. Link: https://lkml.kernel.org/r/20230418074639.1903197-1-senozhatsky@chromium.org Fixes: c0547d0b6a4b ("zsmalloc: consolidate zs_pool's migrate_lock and size_class's locks") Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org> Reviewed-by: Yosry Ahmed <yosryahmed@google.com> Cc: Minchan Kim <minchan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/zsmalloc.c')
-rw-r--r--mm/zsmalloc.c12
1 files changed, 12 insertions, 0 deletions
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index cc81dfba05a0..44ddaf5d601e 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -264,6 +264,7 @@ struct zs_pool {
struct work_struct free_work;
#endif
spinlock_t lock;
+ atomic_t compaction_in_progress;
};
struct zspage {
@@ -2274,6 +2275,15 @@ unsigned long zs_compact(struct zs_pool *pool)
struct size_class *class;
unsigned long pages_freed = 0;
+ /*
+ * Pool compaction is performed under pool->lock so it is basically
+ * single-threaded. Having more than one thread in __zs_compact()
+ * will increase pool->lock contention, which will impact other
+ * zsmalloc operations that need pool->lock.
+ */
+ if (atomic_xchg(&pool->compaction_in_progress, 1))
+ return 0;
+
for (i = ZS_SIZE_CLASSES - 1; i >= 0; i--) {
class = pool->size_class[i];
if (class->index != i)
@@ -2281,6 +2291,7 @@ unsigned long zs_compact(struct zs_pool *pool)
pages_freed += __zs_compact(pool, class);
}
atomic_long_add(pages_freed, &pool->stats.pages_compacted);
+ atomic_set(&pool->compaction_in_progress, 0);
return pages_freed;
}
@@ -2388,6 +2399,7 @@ struct zs_pool *zs_create_pool(const char *name)
init_deferred_free(pool);
spin_lock_init(&pool->lock);
+ atomic_set(&pool->compaction_in_progress, 0);
pool->name = kstrdup(name, GFP_KERNEL);
if (!pool->name)