Re: [PATCH RFC 00/10] Introduce lockless shrink_slab()

[Stephen Rothwell]

Hi Kirill,

On Tue, 07 Aug 2018 18:37:19 +0300 Kirill Tkhai <ktkhai@xxxxxxxxxxxxx> wrote:
>
> After bitmaps of not-empty memcg shrinkers were implemented
> (see "[PATCH v9 00/17] Improve shrink_slab() scalability..."
> series, which is already in mm tree), all the evil in perf
> trace has moved from shrink_slab() to down_read_trylock().
> As reported by Shakeel Butt:
> 
>      > I created 255 memcgs, 255 ext4 mounts and made each memcg create a
>      > file containing few KiBs on corresponding mount. Then in a separate
>      > memcg of 200 MiB limit ran a fork-bomb.
>      >
>      > I ran the "perf record -ag -- sleep 60" and below are the results:
>      > +  47.49%            fb.sh  [kernel.kallsyms]    [k] down_read_trylock
>      > +  30.72%            fb.sh  [kernel.kallsyms]    [k] up_read
>      > +   9.51%            fb.sh  [kernel.kallsyms]    [k] mem_cgroup_iter
>      > +   1.69%            fb.sh  [kernel.kallsyms]    [k] shrink_node_memcg
>      > +   1.35%            fb.sh  [kernel.kallsyms]    [k] mem_cgroup_protected
>      > +   1.05%            fb.sh  [kernel.kallsyms]    [k] queued_spin_lock_slowpath
>      > +   0.85%            fb.sh  [kernel.kallsyms]    [k] _raw_spin_lock
>      > +   0.78%            fb.sh  [kernel.kallsyms]    [k] lruvec_lru_size
>      > +   0.57%            fb.sh  [kernel.kallsyms]    [k] shrink_node
>      > +   0.54%            fb.sh  [kernel.kallsyms]    [k] queue_work_on
>      > +   0.46%            fb.sh  [kernel.kallsyms]    [k] shrink_slab_memcg  
> 
> The patchset continues to improve shrink_slab() scalability and makes
> it lockless completely. Here are several steps for that:

So do you have any numbers for after theses changes?

-- 
Cheers,
Stephen Rothwell

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