linux-kernel - Re: Performance regression in ip_set

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Date: Mon, 15 Jan 2024 14:29:27 +0100
From: Ale Crismani <ale.crismani@...omattic.com>
To: Wang David <00107082@....com>
Cc: Kadlecsik Jozsef <kadlec@...ckhole.kfki.hu>,
 linux-kernel@...r.kernel.org,
 netfilter-devel@...r.kernel.org,
 Ayuso Pablo Neira <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 21:38, Ale Crismani <ale.crismani@...omattic.com> ha scritto:
> 
> 
> 
>> 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


I applied the patch on 6.1.y on top of 875ee3a and I can confirm it fixes the performance issues in our case too.

Thanks once more for having looked at this!
Ale