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

[Kirill Tkhai]

On 08.08.2018 08:39, Shakeel Butt wrote:
> On Tue, Aug 7, 2018 at 6:12 PM Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx> wrote:
>>
>> 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?
>>
> 
> 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
>