lkml.org 
[lkml]   [2017]   [Sep]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] mm: Make count list_lru_one::nr_items lockless
From
Date
On 29.09.2017 00:02, Andrew Morton wrote:
> On Thu, 28 Sep 2017 10:48:55 +0300 Kirill Tkhai <ktkhai@virtuozzo.com> wrote:
>
>>>> This patch aims to make super_cache_count() (and other functions,
>>>> which count LRU nr_items) more effective.
>>>> It allows list_lru_node::memcg_lrus to be RCU-accessed, and makes
>>>> __list_lru_count_one() count nr_items lockless to minimize
>>>> overhead introduced by locking operation, and to make parallel
>>>> reclaims more scalable.
>>>
>>> And... what were the effects of the patch? Did you not run the same
>>> performance tests after applying it?
>>
>> I've just detected the such high usage of shrink slab on production node. It's rather
>> difficult to make it use another kernel, than it uses, only kpatches are possible.
>> So, I haven't estimated how it acts on node's performance.
>> On test node I see, that the patch obviously removes raw_spin_lock from perf profile.
>> So, it's a little bit untested in this way.
>
> Well that's a problem. The patch increases list_lru.o text size by a
> lot (4800->5696) which will have a cost. And we don't have proof that
> any benefit is worth that cost. It shouldn't be too hard to cook up a
> synthetic test to trigger memcg slab reclaim and then run a
> before-n-after benchmark?

Ok, then, please, ignore this for a while, I'll try to do it a little bit later.

Kirill

\
 
 \ /
  Last update: 2017-09-29 10:16    [W:0.065 / U:0.044 seconds]
©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site