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Subject: Re: [PATCH RFC 00/10] Introduce lockless shrink_slab()
To:     Shakeel Butt <shakeelb@google.com>,
        Stephen Rothwell <sfr@canb.auug.org.au>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        gregkh@linuxfoundation.org, rafael@kernel.org,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        "Darrick J. Wong" <darrick.wong@oracle.com>,
        Paul McKenney <paulmck@linux.vnet.ibm.com>,
        josh@joshtriplett.org, Steven Rostedt <rostedt@goodmis.org>,
        mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com,
        Hugh Dickins <hughd@google.com>, shuah@kernel.org,
        robh@kernel.org, ulf.hansson@linaro.org, aspriel@gmail.com,
        vivek.gautam@codeaurora.org, robin.murphy@arm.com, joe@perches.com,
        heikki.krogerus@linux.intel.com,
        Vladimir Davydov <vdavydov.dev@gmail.com>,
        Michal Hocko <mhocko@suse.com>,
        Chris Wilson <chris@chris-wilson.co.uk>,
        Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
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        Huang Ying <ying.huang@intel.com>, jbacik@fb.com,
        Ingo Molnar <mingo@kernel.org>, mhiramat@kernel.org,
        LKML <linux-kernel@vger.kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
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From:   Kirill Tkhai <ktkhai@virtuozzo.com>
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Date:   Wed, 8 Aug 2018 13:18:24 +0300
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On 08.08.2018 08:39, Shakeel Butt wrote:
> On Tue, Aug 7, 2018 at 6:12 PM Stephen Rothwell <sfr@canb.auug.org.au> wrote:
>>
>> Hi Kirill,
>>
>> On Tue, 07 Aug 2018 18:37:19 +0300 Kirill Tkhai <ktkhai@virtuozzo.com> 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?
>>
> 
> I will do the same experiment as before with these patches sometime
> this or next week.

Thanks, Shakeel!

> BTW Kirill, thanks for pushing this.
> 
> regards,
> Shakeel
>