From: Joel Fernandes <joel@joelfernandes.org>
To: Michal Hocko <mhocko@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org,
Alexey Dobriyan <adobriyan@gmail.com>,
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>,
minchan@kernel.org, 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 1/6] mm/page_idle: Add per-pid idle page tracking using virtual index
Date: Tue, 13 Aug 2019 10:45:17 -0400 [thread overview]
Message-ID: <20190813144517.GE258732@google.com> (raw)
In-Reply-To: <20190813141432.GL17933@dhcp22.suse.cz>
On Tue, Aug 13, 2019 at 04:14:32PM +0200, Michal Hocko wrote:
[snip]
> > > If the API is flawed then this is likely going
> > > to kick us later and will be hard to fix. I am still not convinced about
> > > the swap part of the thing TBH.
> >
> > Ok, then let us discuss it. As I mentioned before, without this we lose the
> > access information due to MADVISE or swapping. Minchan and Konstantin both
> > suggested it that's why I also added it (other than me also realizing that it
> > is neeed).
>
> I have described my concerns about the general idle bit behavior after
> unmapping pointing to discrepancy with !anon pages. And I believe those
> haven't been addressed yet.
You are referring to this post right?
https://lkml.org/lkml/2019/8/6/637
Specifically your question was:
How are you going to handle situation when the page is unmapped and refaulted again (e.g. a normal reclaim of a pagecache)?
Currently I don't know how to implement that. Would it work if I stored the
page-idle bit information in the pte of the file page (after the page is
unmapped by reclaim?).
Also, this could be a future extension - the Android heap profiler does not
need it right now. I know that's not a good argument but it is useful to say
that it doesn't affect a real world usecase.. the swap issue on the other
hand, is a real usecase. Since the profiler should not get affected by
swapping or MADVISE_COLD hints.
> Besides that I am still not seeing any
> description of the usecase that would suffer from the lack of the
> functionality in changelogs.
You are talking about the swap usecase? The usecase is well layed out in v5
2/6. Did you see it? https://lore.kernel.org/patchwork/patch/1112283/
thanks,
- Joel
next prev parent reply other threads:[~2019-08-13 14:45 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
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 [this message]
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
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