From: Joel Fernandes <joel@joelfernandes.org>
To: Michal Hocko <mhocko@kernel.org>, khlebnikov@yandex-team.ru
Cc: linux-kernel@vger.kernel.org, Minchan Kim <minchan@kernel.org>,
Alexey Dobriyan <adobriyan@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Borislav Petkov <bp@alien8.de>,
Brendan Gregg <bgregg@netflix.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Christian Hansen <chansen3@cisco.com>,
dancol@google.com, fmayer@google.com,
"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
Jonathan Corbet <corbet@lwn.net>,
Kees Cook <keescook@chromium.org>,
kernel-team@android.com, linux-api@vger.kernel.org,
linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, Mike Rapoport <rppt@linux.ibm.com>,
namhyung@google.com, paulmck@linux.ibm.com,
Robin Murphy <robin.murphy@arm.com>, Roman Gushchin <guro@fb.com>,
Stephen Rothwell <sfr@canb.auug.org.au>,
surenb@google.com, Thomas Gleixner <tglx@linutronix.de>,
tkjos@google.com, Vladimir Davydov <vdavydov.dev@gmail.com>,
Vlastimil Babka <vbabka@suse.cz>, Will Deacon <will@kernel.org>
Subject: Re: [PATCH v5 2/6] mm/page_idle: Add support for handling swapped PG_Idle pages
Date: Tue, 13 Aug 2019 11:36:59 -0400 [thread overview]
Message-ID: <20190813153659.GD14622@google.com> (raw)
In-Reply-To: <20190813150450.GN17933@dhcp22.suse.cz>
On Tue, Aug 13, 2019 at 05:04:50PM +0200, Michal Hocko wrote:
> On Wed 07-08-19 13:15:55, Joel Fernandes (Google) wrote:
> > Idle page tracking currently does not work well in the following
> > scenario:
> > 1. mark page-A idle which was present at that time.
> > 2. run workload
> > 3. page-A is not touched by workload
> > 4. *sudden* memory pressure happen so finally page A is finally swapped out
> > 5. now see the page A - it appears as if it was accessed (pte unmapped
> > so idle bit not set in output) - but it's incorrect.
> >
> > To fix this, we store the idle information into a new idle bit of the
> > swap PTE during swapping of anonymous pages.
> >
> > Also in the future, madvise extensions will allow a system process
> > manager (like Android's ActivityManager) to swap pages out of a process
> > that it knows will be cold. To an external process like a heap profiler
> > that is doing idle tracking on another process, this procedure will
> > interfere with the idle page tracking similar to the above steps.
>
> This could be solved by checking the !present/swapped out pages
> right? Whoever decided to put the page out to the swap just made it
> idle effectively. So the monitor can make some educated guess for
> tracking. If that is fundamentally not possible then please describe
> why.
But the monitoring process (profiler) does not have control over the 'whoever
made it effectively idle' process.
As you said it will be a guess, it will not be accurate.
I am curious what is your concern with using a bit in the swap PTE?
(Adding Konstantin as well since we may be interested in this, since we also
suggested this idea).
thanks,
- Joel
next prev parent reply other threads:[~2019-08-13 15:37 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-07 17:15 [PATCH v5 1/6] mm/page_idle: Add per-pid idle page tracking using virtual index Joel Fernandes (Google)
2019-08-07 17:15 ` [PATCH v5 2/6] mm/page_idle: Add support for handling swapped PG_Idle pages Joel Fernandes (Google)
2019-08-13 15:04 ` Michal Hocko
2019-08-13 15:36 ` Joel Fernandes [this message]
2019-08-13 19:24 ` Konstantin Khlebnikov
2019-08-14 8:05 ` Michal Hocko
2019-08-14 16:32 ` Joel Fernandes
2019-08-14 18:36 ` Michal Hocko
2019-08-07 17:15 ` [PATCH v5 3/6] [RFC] x86: Add support for idle bit in swap PTE Joel Fernandes (Google)
2019-08-07 17:15 ` [PATCH v5 4/6] [RFC] arm64: " Joel Fernandes (Google)
2019-08-07 17:15 ` [PATCH v5 5/6] page_idle: Drain all LRU pagevec before idle tracking Joel Fernandes (Google)
2019-08-07 17:15 ` [PATCH v5 6/6] doc: Update documentation for page_idle virtual address indexing Joel Fernandes (Google)
2019-08-07 20:04 ` [PATCH v5 1/6] mm/page_idle: Add per-pid idle page tracking using virtual index Andrew Morton
2019-08-07 20:45 ` Joel Fernandes
2019-08-07 20:58 ` Andrew Morton
2019-08-07 21:31 ` Joel Fernandes
2019-08-07 21:55 ` Joel Fernandes
2019-08-08 8:00 ` Michal Hocko
2019-08-12 14:56 ` Joel Fernandes
2019-08-13 9:14 ` Michal Hocko
2019-08-13 13:51 ` Joel Fernandes
2019-08-13 14:14 ` Michal Hocko
2019-08-13 14:45 ` Joel Fernandes
2019-08-13 14:57 ` Michal Hocko
2019-08-12 18:14 ` Jann Horn
2019-08-13 10:08 ` Michal Hocko
2019-08-13 14:25 ` Joel Fernandes
2019-08-13 15:19 ` Jann Horn
2019-08-13 15:29 ` Jann Horn
2019-08-13 15:34 ` Daniel Gruss
2019-08-13 19:18 ` Joel Fernandes
2019-08-14 7:56 ` Michal Hocko
2019-08-19 21:52 ` Joel Fernandes
2019-08-13 15:30 ` Joel Fernandes
2019-08-13 15:40 ` Jann Horn
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190813153659.GD14622@google.com \
--to=joel@joelfernandes.org \
--cc=adobriyan@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=bgregg@netflix.com \
--cc=bp@alien8.de \
--cc=catalin.marinas@arm.com \
--cc=chansen3@cisco.com \
--cc=corbet@lwn.net \
--cc=dancol@google.com \
--cc=fmayer@google.com \
--cc=guro@fb.com \
--cc=hpa@zytor.com \
--cc=keescook@chromium.org \
--cc=kernel-team@android.com \
--cc=khlebnikov@yandex-team.ru \
--cc=linux-api@vger.kernel.org \
--cc=linux-doc@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mhocko@kernel.org \
--cc=minchan@kernel.org \
--cc=mingo@redhat.com \
--cc=namhyung@google.com \
--cc=paulmck@linux.ibm.com \
--cc=robin.murphy@arm.com \
--cc=rppt@linux.ibm.com \
--cc=sfr@canb.auug.org.au \
--cc=surenb@google.com \
--cc=tglx@linutronix.de \
--cc=tkjos@google.com \
--cc=vbabka@suse.cz \
--cc=vdavydov.dev@gmail.com \
--cc=will@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).