linux-kernel - Re: [PATCH 0/9] mm/madvise: batch tlb flushes for MADV_DONTNEED and MADV

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Message-ID: <mecl3oimrbzeh3o2gaolmpqeyw7f7npme4zhpnzkqohrgxwotq@qssi4idgvftl>
Date: Mon, 10 Mar 2025 16:15:06 -0700
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: SeongJae Park <sj@...nel.org>, "Liam R. Howlett" <howlett@...il.com>, 
	David Hildenbrand <david@...hat.com>, Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, 
	Vlastimil Babka <vbabka@...e.cz>, kernel-team@...a.com, linux-kernel@...r.kernel.org, 
	linux-mm@...ck.org
Subject: Re: [PATCH 0/9] mm/madvise: batch tlb flushes for MADV_DONTNEED and
 MADV_FREE

On Mon, Mar 10, 2025 at 03:39:21PM -0700, Andrew Morton wrote:
> On Mon, 10 Mar 2025 10:23:09 -0700 SeongJae Park <sj@...nel.org> wrote:
> 
> >  It is unclear if such use case
> > is common and the inefficiency is significant. 
> 
> Well, we could conduct a survey,
> 
> Can you add some logging to detect when userspace performs such an
> madvise() call, then run that kernel on some "typical" machines which
> are running "typical" workloads?  That should give us a feeling for how
> often userspace does this, and hence will help us understand the usefulness
> of this patchset.

Just for the clarification, this patchset is very useful for the
process_madvise() and the experiment results show that. I think what SJ
wants to say is specific to madvise() syscall that this change might or
might not be that helpful. It will be helpful if the user application is
madvising regions comprising of multiple vmas. However this patchset is
very very useful for process_madvise().