linux-kernel - Re: Performance regression in ip_set

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Date: Sun, 14 Jan 2024 21:38:05 +0100
From: Ale Crismani <ale.crismani@...omattic.com>
To: David Wang <00107082@....com>
Cc: Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>,
 linux-kernel@...r.kernel.org,
 netfilter-devel@...r.kernel.org,
 Pablo Neira Ayuso <pablo@...filter.org>,
 xiaolinkui@...inos.cn
Subject: Re: Performance regression in ip_set_swap on 6.7.0



> Il giorno 14 gen 2024, alle ore 06:30, David Wang <00107082@....com> ha scritto:
> 
> 
> At 2024-01-14 02:24:07, "Jozsef Kadlecsik" <kadlec@...ckhole.kfki.hu> wrote:
>> On Thu, 11 Jan 2024, David Wang wrote:
>> 
>>> I tested the patch with code stressing swap->destroy->create->add 10000 
>>> times, the performance regression still happens, and now it is 
>>> ip_set_destroy. (I pasted the test code at the end of this mail)
> 
>>> 
>>> They all call wait_for_completion, which may sleep on something on 
>>> purpose, I guess...
>> 
>> That's OK because ip_set_destroy() calls rcu_barrier() which is needed to 
>> handle flush in list type of sets.
>> 
>> However, rcu_barrier() with call_rcu() together makes multiple destroys 
>> one after another slow. But rcu_barrier() is needed for list type of sets 
>> only and that can be handled separately. So could you test the patch 
>> below? According to my tests it is even a little bit faster than the 
>> original code before synchronize_rcu() was added to swap.
> 
> Confirmed~! This patch does fix the performance regression in my case.
> 
> Hope it can fix ale.crismani@...omattic.com's original issue.
> 
> 
> 
> Thanks~
> David


Thanks for all the help on this, I'll try the patch tomorrow hopefully and will report back!

best wishes,
Ale