linux-kernel - Re: [linus:master] [mseal] 8be7258aad: stress-ng.pagemove.page_remaps_per

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Message-ID: <CAKbZUD1278Bq+5QwjH=LeYSgcugZ3JbvkLeoB3whei_gkEXV+w@mail.gmail.com>
Date: Tue, 6 Aug 2024 22:37:08 +0100
From: Pedro Falcato <pedro.falcato@...il.com>
To: Oliver Sang <oliver.sang@...el.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>, Jeff Xu <jeffxu@...gle.com>, 
	Michael Ellerman <mpe@...erman.id.au>, Nicholas Piggin <npiggin@...il.com>, 
	Christophe Leroy <christophe.leroy@...roup.eu>, Jeff Xu <jeffxu@...omium.org>, 
	oe-lkp@...ts.linux.dev, lkp@...el.com, linux-kernel@...r.kernel.org, 
	Andrew Morton <akpm@...ux-foundation.org>, Kees Cook <keescook@...omium.org>, 
	"Liam R. Howlett" <Liam.Howlett@...cle.com>, Dave Hansen <dave.hansen@...el.com>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Guenter Roeck <groeck@...omium.org>, 
	Jann Horn <jannh@...gle.com>, Jonathan Corbet <corbet@....net>, 
	Jorge Lucangeli Obes <jorgelo@...omium.org>, Matthew Wilcox <willy@...radead.org>, 
	Muhammad Usama Anjum <usama.anjum@...labora.com>, Stephen Röttger <sroettger@...gle.com>, 
	Suren Baghdasaryan <surenb@...gle.com>, Amer Al Shanawany <amer.shanawany@...il.com>, 
	Javier Carrasco <javier.carrasco.cruz@...il.com>, Shuah Khan <shuah@...nel.org>, 
	linux-api@...r.kernel.org, linux-mm@...ck.org, ying.huang@...el.com, 
	feng.tang@...el.com, fengwei.yin@...el.com
Subject: Re: [linus:master] [mseal] 8be7258aad: stress-ng.pagemove.page_remaps_per_sec
 -4.4% regression

On Tue, Aug 6, 2024 at 7:05 AM Oliver Sang <oliver.sang@...el.com> wrote:
>
> hi, Linus,
>
> On Mon, Aug 05, 2024 at 12:33:58PM -0700, Linus Torvalds wrote:
> > On Mon, 5 Aug 2024 at 11:55, Linus Torvalds
> > <torvalds@...ux-foundation.org> wrote:
> > >
> > > So please consider this a "maybe something like this" patch, but that
> > > 'arch_unmap()' really is pretty nasty
> >
> > Actually, the whole powerpc vdso code confused me. It's not the vvar
> > thing that wants this close thing, it's the other ones that have the
> > remap thing.
> >
> > .. and there were two of those error cases that needed to reset the
> > vdso pointer.
> >
> > That all shows just how carefully I was reading this code.
> >
> > New version - still untested, but now I've read through it one more
> > time - attached.
>
> we tested this version by applying it directly upon 8be7258aad,  but seems it
> have little impact to performance. still similar regression if comparing to
> ff388fe5c4.

Hi,

I've just sent out a patch set[1] that should alleviate (or hopefully
totally fix) these performance regressions. It'd be great if you could
test it.

For everyone: Apologies if you're in the CC list and I didn't CC you,
but I tried to keep my patch set's CC list relatively short and clean
(and I focused on the active participants).
Everyone's comments are very welcome.

[1]: https://lore.kernel.org/all/20240806212808.1885309-1-pedro.falcato@gmail.com/
-- 
Pedro