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

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Message-ID: <Z893lHkRWhHDuWUC@google.com>
Date: Mon, 10 Mar 2025 23:36:52 +0000
From: Roman Gushchin <roman.gushchin@...ux.dev>
To: Shakeel Butt <shakeel.butt@...ux.dev>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	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 04:15:06PM -0700, Shakeel Butt wrote:
> 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.

+1

Google carried an internal version for a vectorized madvise() which
was much faster than process_madvise() last time I measured it.
I hope SJ's patchset will (partially) address this difference,
which will hopefully allow to drop the internal implementation
for process_madvise.