linux-kernel - Re: [RFC PATCH v1] mm: improve call_controls

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Message-ID: <20251231050138.77727-1-sj@kernel.org>
Date: Tue, 30 Dec 2025 21:01:37 -0800
From: SeongJae Park <sj@...nel.org>
To: Gutierrez Asier <gutierrez.asier@...wei-partners.com>
Cc: SeongJae Park <sj@...nel.org>,
	akpm@...ux-foundation.org,
	damon@...ts.linux.dev,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	wangkefeng.wang@...wei.com,
	artem.kuzin@...wei.com,
	stepanov.anatoly@...wei.com
Subject: Re: [RFC PATCH v1] mm: improve call_controls_lock

On Tue, 30 Dec 2025 12:02:31 +0300 Gutierrez Asier <gutierrez.asier@...wei-partners.com> wrote:

> 
> 
> On 12/29/2025 6:22 PM, SeongJae Park wrote:
> > Hello Asier,
> 
> Hi SeongJae,
> 
> > 
> > Thank you for sending this patch!
> > 
> > On Mon, 29 Dec 2025 14:55:32 +0000 Asier Gutierrez <gutierrez.asier@...wei-partners.com> wrote:
> > 
> >> This is a minor patch set for a call_controls_lock synchronization improvement.
> > 
> > Please break description lines to not exceed 75 characters per line.
> > 
> >>
> >> Spinlocks are faster than mutexes, even when the mutex takes the fast
> >> path. Hence, this patch replaces the mutex call_controls_lock with a spinlock.
> > 
> > But call_controls_lock is not being used on performance critical part.
> > Actually, most of DAMON code is not performance critical.  I really appreciate
> > your patch, but I have to say I don't think this change is really needed now.
> > Please let me know if I'm missing something.
> 
> I was just reviewing the code and I noticed this. Yes, you are right, the performance 
> is not critical.

Thank you for flexibly accepting my humble opinion.

> 
> >>
> >> Initial benchmarking shows the following results
> >>
> >>
> >> # bpftrace -e 'kprobe:kdamond_call { @start[tid] = nsecs; }
> > 
> > Commit log shouldn't start with '#'.  Please consider indenting the above
> > command and below outputs of it.
> > 
> > 
> > Thanks,
> > SJ
> > 
> > [...]
> > 
> 
> Thanks a lot for the review!

My pleasure!  Looking forward to your next patch :)


Thanks,
SJ

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