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Date:   Wed, 8 Aug 2018 11:12:24 +1000
From:   Stephen Rothwell <sfr@canb.auug.org.au>
To:     Kirill Tkhai <ktkhai@virtuozzo.com>
Cc:     akpm@linux-foundation.org, gregkh@linuxfoundation.org,
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Subject: Re: [PATCH RFC 00/10] Introduce lockless shrink_slab()
Message-ID: <20180808111224.52a451d9@canb.auug.org.au>
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Hi Kirill,

On Tue, 07 Aug 2018 18:37:19 +0300 Kirill Tkhai <ktkhai@virtuozzo.com> wrot=
e:
>
> 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:
>=20
>      > 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_try=
lock
>      > +  30.72%            fb.sh  [kernel.kallsyms]    [k] up_read
>      > +   9.51%            fb.sh  [kernel.kallsyms]    [k] mem_cgroup_it=
er
>      > +   1.69%            fb.sh  [kernel.kallsyms]    [k] shrink_node_m=
emcg
>      > +   1.35%            fb.sh  [kernel.kallsyms]    [k] mem_cgroup_pr=
otected
>      > +   1.05%            fb.sh  [kernel.kallsyms]    [k] queued_spin_l=
ock_slowpath
>      > +   0.85%            fb.sh  [kernel.kallsyms]    [k] _raw_spin_lock
>      > +   0.78%            fb.sh  [kernel.kallsyms]    [k] lruvec_lru_si=
ze
>      > +   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_m=
emcg =20
>=20
> 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?

--=20
Cheers,
Stephen Rothwell

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