From: Hugh Dickins <hughd@google.com>
To: CGEL <cgel.zte@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>,
akpm@linux-foundation.org, sfr@canb.auug.org.au,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Yang Yang <yang.yang29@zte.com.cn>
Subject: Re: [PATCH] psi: Treat ksm swapping in copy as memstall
Date: Mon, 7 Feb 2022 19:22:22 -0800 (PST) [thread overview]
Message-ID: <72532675-d898-9f30-1ba4-318fbd61786@google.com> (raw)
In-Reply-To: <61f35591.1c69fb81.48dad.3244@mx.google.com>
On Fri, 28 Jan 2022, CGEL wrote:
> On Thu, Jan 27, 2022 at 08:29:08PM -0500, Johannes Weiner wrote:
> > On Fri, Jan 21, 2022 at 09:51:08AM +0000, CGEL wrote:
> > > Wed, Jan 19, 2022 at 07:58:23AM -0500, Johannes Weiner wrote:
> > > > On Wed, Jan 19, 2022 at 06:13:54AM +0000, CGEL wrote:
> > > > > I did a test, when we use zram, it takes longer time for ksm copying than
> > > > > swap_readpage(). Ksm copying average takes 147263ns, swap_readpage()
> > > > > average takes 55639ns. So I think this patch is reasonable.
> > > >
> > > > Ok, that sounds reasonable to me as well. Please add the
> > > > PageWorkingset() check and resubmit the patch. Thanks!
> > > I am a litte confused about adding PageWorkingset(), since I
> > > think ksm_might_need_to_copy() memstall is like swap_readpage()
> > > memstall and swap_readpage() doesn't add PageWorkingset().
> >
> > That's actually a bug! It should do that.
> I recently found that too. Please CC to me your new patch, thanks!
> And I will send V2 of this patch "psi: Treat ksm swapping in copy
> as memstall" with PageWorkingset().
I'm entirely PSI-ignorant, and reluctant to disagree with Johannes,
but I don't see how your patch to ksm_might_need_to_copy() could be
correct - maybe the "swapping" in your subject is confusing.
There is no PSI enter and exit around the page allocation and copying
in wp_page_copy(), so why in the analogous ksm_might_need_to_copy()?
Hugh
next prev parent reply other threads:[~2022-02-08 3:22 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-16 15:21 [PATCH] psi: Treat ksm swapping in copy as memstall cgel.zte
2022-01-17 12:14 ` Johannes Weiner
2022-01-19 6:13 ` CGEL
2022-01-19 12:58 ` Johannes Weiner
2022-01-21 9:51 ` CGEL
2022-01-28 1:29 ` Johannes Weiner
2022-01-28 2:31 ` CGEL
2022-02-08 3:22 ` Hugh Dickins [this message]
2022-02-08 13:09 ` CGEL
2022-02-09 5:55 ` Hugh Dickins
2022-02-10 6:52 ` CGEL
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