mirrors/linux
1
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git synced 2025-12-27 11:06:41 -05:00
Code Issues Packages Projects Releases Wiki Activity

memcg: optimize exit to user space

Browse Source 
memcg uses TIF_NOTIFY_RESUME to handle reclaiming on exit to user space. 
TIF_NOTIFY_RESUME is a multiplexing TIF bit, which is utilized by other
entities as well.

This results in a unconditional mem_cgroup_handle_over_high() call for
every invocation of resume_user_mode_work(), which is a pointless exercise
as most of the time there is no reclaim work to do.

Especially since RSEQ is used by glibc, TIF_NOTIFY_RESUME is raised quite
frequently and the empty calls show up in exit path profiling.

Optimize this by doing a quick check of the reclaim condition before
invoking it.

[akpm@linux-foundation.org: remove now-unneeded test of memcg_nr_pages_over_high==0, per Shakeel]
Link: https://lkml.kernel.org/r/87tt2b6zgs.ffs@tglx
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Thomas Gleixner
2025-08-13 16:57:55 +02:00
committed by Andrew Morton
parent 868ade323e
commit ec45783fce
2 changed files with 9 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
include/linux/memcontrol.h
View File

@@ -900,7 +900,13 @@ unsigned long mem_cgroup_get_zone_lru_size(struct lruvec *lruvec,
return READ_ONCE(mz->lru_zone_size[zone_idx][lru]);
}
void mem_cgroup_handle_over_high(gfp_t gfp_mask);
void __mem_cgroup_handle_over_high(gfp_t gfp_mask);
static inline void mem_cgroup_handle_over_high(gfp_t gfp_mask)
{
if (unlikely(current->memcg_nr_pages_over_high))
__mem_cgroup_handle_over_high(gfp_mask);
}
unsigned long mem_cgroup_get_max(struct mem_cgroup *memcg);

7
mm/memcontrol.c
View File

@@ -2203,7 +2203,7 @@ static unsigned long calculate_high_delay(struct mem_cgroup *memcg,
* try_charge() (context permitting), as well as from the userland
* return path where reclaim is always able to block.
*/
void mem_cgroup_handle_over_high(gfp_t gfp_mask)
void __mem_cgroup_handle_over_high(gfp_t gfp_mask)
{
unsigned long penalty_jiffies;
unsigned long pflags;
@@ -2213,9 +2213,6 @@ void mem_cgroup_handle_over_high(gfp_t gfp_mask)
struct mem_cgroup *memcg;
bool in_retry = false;
if (likely(!nr_pages))
return;
memcg = get_mem_cgroup_from_mm(current->mm);
current->memcg_nr_pages_over_high = 0;
@@ -2486,7 +2483,7 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask,
if (current->memcg_nr_pages_over_high > MEMCG_CHARGE_BATCH &&
!(current->flags & PF_MEMALLOC) &&
gfpflags_allow_blocking(gfp_mask))
mem_cgroup_handle_over_high(gfp_mask);
__mem_cgroup_handle_over_high(gfp_mask);
return 0;
}