On Fri 02-04-21 18:38:54, Neil Sun wrote:
> This patch makes shrink_slab() with task's memcg in drop_slab_node(),
> so we can free reclaimable slab objects belongs to memcg /lxc/i-vbe1u8o7
> with following command:
You are changing semantic of the existing user interface. This knob has
never been memcg aware and it is supposed to have a global impact. I do
not think we can simply change that without some users being surprised
or even breaking them.
> cgexec -g memory:/lxc/i-vbe1u8o7 sysctl vm.drop_caches=2
>
> Test with following steps:
>
> root@i-yl0pwrt8:~# free -h
> total used free shared buff/cache available
> Mem: 62Gi 265Mi 62Gi 1.0Mi 290Mi 61Gi
> Swap: 31Gi 0B 31Gi
> root@i-yl0pwrt8:~# (cd /tmp && /root/generate_slab_cache)
> root@i-yl0pwrt8:~# free -h
> total used free shared buff/cache available
> Mem: 62Gi 266Mi 60Gi 1.0Mi 2.2Gi 61Gi
> Swap: 31Gi 0B 31Gi
> root@i-yl0pwrt8:~# cgcreate -g memory:/lxc/i-vbe1u8o7
> root@i-yl0pwrt8:~# cgexec -g memory:/lxc/i-vbe1u8o7 /root/generate_slab_cache
> root@i-yl0pwrt8:~# free -h
> total used free shared buff/cache available
> Mem: 62Gi 267Mi 58Gi 1.0Mi 4.1Gi 61Gi
> Swap: 31Gi 0B 31Gi
> root@i-yl0pwrt8:~# cgexec -g memory:/lxc/i-vbe1u8o7 sysctl vm.drop_caches=2
> vm.drop_caches = 2
> root@i-yl0pwrt8:~# free -h
> total used free shared buff/cache available
> Mem: 62Gi 268Mi 60Gi 1.0Mi 2.2Gi 61Gi
> Swap: 31Gi 0B 31Gi
> root@i-yl0pwrt8:~# sysctl vm.drop_caches=2
> vm.drop_caches = 2
> root@i-yl0pwrt8:~# free -h
> total used free shared buff/cache available
> Mem: 62Gi 267Mi 62Gi 1.0Mi 290Mi 61Gi
> Swap: 31Gi 0B 31Gi
>
> Signed-off-by: Neil Sun <neilsun@xxxxxxxxxx>
> ---
> mm/vmscan.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 562e87cb..81d770a 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -702,7 +702,7 @@ void drop_slab_node(int nid)
> return;
>
> freed = 0;
> - memcg = mem_cgroup_iter(NULL, NULL, NULL);
> + memcg = mem_cgroup_from_task(current);
> do {
> freed += shrink_slab(GFP_KERNEL, nid, memcg, 0);
> } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
> --
> 2.7.4
--
Michal Hocko
SUSE Labs
