[1] Provides a way for user-space to trigger proactive reclaim by introducing a write-only memcg file 'memory.reclaim'. However reclaim stats like number of pages scanned and reclaimed is still not directly available to the user-space. This patch proposes to extend [1] to make the memcg file 'memory.reclaim' readable which returns the number of pages scanned / reclaimed during the reclaim process from 'struct vmpressure' associated with each memcg. This should let user-space asses how successful proactive reclaim triggered from memcg 'memory.reclaim' was ? With the patch following command flow is expected: # echo "1M" > memory.reclaim # cat memory.reclaim scanned 76 reclaimed 32 [1]: https://lore.kernel.org/r/20220425190040.2475377-1-yosryahmed@xxxxxxxxxx Cc: Shakeel Butt <shakeelb@xxxxxxxxxx> Cc: Yosry Ahmed <yosryahmed@xxxxxxxxxx> Signed-off-by: Vaibhav Jain <vaibhav@xxxxxxxxxxxxx> --- Documentation/admin-guide/cgroup-v2.rst | 15 ++++++++++++--- mm/memcontrol.c | 14 ++++++++++++++ 2 files changed, 26 insertions(+), 3 deletions(-) diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst index 27ebef2485a3..44610165261d 100644 --- a/Documentation/admin-guide/cgroup-v2.rst +++ b/Documentation/admin-guide/cgroup-v2.rst @@ -1209,18 +1209,27 @@ PAGE_SIZE multiple when read back. utility is limited to providing the final safety net. memory.reclaim - A write-only nested-keyed file which exists for all cgroups. + A nested-keyed file which exists for all cgroups. - This is a simple interface to trigger memory reclaim in the - target cgroup. + This is a simple interface to trigger memory reclaim and retrieve + reclaim stats in the target cgroup. This file accepts a single key, the number of bytes to reclaim. No nested keys are currently supported. + Reading the file returns number of pages scanned and number of + pages reclaimed from the memcg. This information fetched from + vmpressure info associated with each cgroup. + Example:: echo "1G" > memory.reclaim + cat memory.reclaim + + scanned 78 + reclaimed 30 + The interface can be later extended with nested keys to configure the reclaim behavior. For example, specify the type of memory to reclaim from (anon, file, ..). diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 2e2bfbed4717..9e43580a8726 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -6423,6 +6423,19 @@ static ssize_t memory_oom_group_write(struct kernfs_open_file *of, return nbytes; } +static int memory_reclaim_show(struct seq_file *m, void *v) +{ + struct mem_cgroup *memcg = mem_cgroup_from_seq(m); + struct vmpressure *vmpr = memcg_to_vmpressure(memcg); + + spin_lock(&vmpr->sr_lock); + seq_printf(m, "scanned %lu\nreclaimed %lu\n", + vmpr->scanned, vmpr->reclaimed); + spin_unlock(&vmpr->sr_lock); + + return 0; +} + static ssize_t memory_reclaim(struct kernfs_open_file *of, char *buf, size_t nbytes, loff_t off) { @@ -6525,6 +6538,7 @@ static struct cftype memory_files[] = { .name = "reclaim", .flags = CFTYPE_NS_DELEGATABLE, .write = memory_reclaim, + .seq_show = memory_reclaim_show, }, { } /* terminate */ }; -- 2.35.1
