linux-kernel - Re:Re: [PATCH] Add accumulated call counter for memory allocation profiling

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Message-ID: <13c19bd1.2c49.1906c1ac5bf.Coremail.00107082@163.com>
Date: Mon, 1 Jul 2024 10:23:32 +0800 (CST)
From: "David Wang" <00107082@....com>
To: "Suren Baghdasaryan" <surenb@...gle.com>
Cc: kent.overstreet@...ux.dev, akpm@...ux-foundation.org, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org
Subject: Re:Re: [PATCH] Add accumulated call counter for memory allocation
 profiling

HI Suren, 

At 2024-07-01 03:33:14, "Suren Baghdasaryan" <surenb@...gle.com> wrote:
>On Mon, Jun 17, 2024 at 8:33 AM David Wang <00107082@....com> wrote:
>>
>> Accumulated call counter can be used to evaluate rate
>> of memory allocation via delta(counters)/delta(time).
>> This metrics can help analysis performance behaviours,
>> e.g. tuning cache size, etc.
>
>Sorry for the delay, David.
>IIUC with this counter you can identify the number of allocations ever
>made from a specific code location. Could you please clarify the usage
>a bit more? Is the goal to see which locations are the most active and
>the rate at which allocations are made there? How will that
>information be used?

Cumulative counters can be sampled with timestamp,  say at T1, a monitoring tool got a sample value V1,
then after sampling interval, at T2,  got a sample value V2. Then the average rate of allocation can be evaluated
via (V2-V1)/(T2-T1). (The accuracy depends on sampling interval)

This information "may" help identify where the memory allocation is unnecessary frequent,  
and  gain some  better performance by making less memory allocation .
The performance "gain" is just a guess, I do not have a valid example.

>I'm a bit cautious here because each counter will take more space and
>use some additional cpu cycles.
>Thanks,
>Suren.
>

Thanks~!
David