linux-kernel - Re: [PATCH] x86/split_lock: add split lock counter

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Message-ID: <039b8ba2-09c8-487d-b2ef-f74d6ab4e489@yandex-team.ru>
Date: Sat, 16 Dec 2023 13:56:05 +0300
From: Maksim Davydov <davydov-max@...dex-team.ru>
To: Dave Hansen <dave.hansen@...el.com>
Cc: den-plotnikov@...dex-team.ru, tony.luck@...el.com,
 linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
 bp@...en8.de, dave.hansen@...ux.intel.com, hpa@...or.com,
 peterz@...radead.org, juri.lelli@...hat.com, vincent.guittot@...aro.org,
 x86@...nel.org
Subject: Re: [PATCH] x86/split_lock: add split lock counter


On 12/15/23 21:16, Dave Hansen wrote:
> On 12/15/23 06:01, Maksim Davydov wrote:
>> Provides per task split locks counter to monitor split locks rate
>> in the system. It can be helpful in split locks monitoring to get a clear
>> sense of which process causing split locks and how many of them have
>> happened by the moment. For instance, it might be used by cloud providers
>> who can't control guest executable code and want to make decisions based
>> on the rate value like ratelimiting or notifing the split lock origins.
> Have you considered doing this with tracing instead?
>
> It seems a _little_ silly for everyone to pay the cost of having that
> counter around.
No, it just seemed like a good idea to make a simple machine-readable
interface based on the existing flag (reported_split_lock).
What if this interface is made together with the appropriate CONFIG flag
(default false)? Thus it won't affect those who don't need it.

-- 
Best regards,
Maksim Davydov