From: Sanjay Ghemawat <sanjay@google.com>
To: Minchan Kim <minchan@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Michael Kerrisk <mtk.manpages@gmail.com>,
Arun Sharma <asharma@fb.com>, Paul Turner <pjt@google.com>,
David Rientjes <rientjes@google.com>,
John Stultz <john.stultz@linaro.org>,
Christoph Lameter <cl@linux.com>,
Android Kernel Team <kernel-team@android.com>,
Robert Love <rlove@google.com>, Mel Gorman <mel@csn.ul.ie>,
Hugh Dickins <hughd@google.com>,
Dave Hansen <dave@linux.vnet.ibm.com>,
Rik van Riel <riel@redhat.com>,
Dave Chinner <david@fromorbit.com>, Neil Brown <neilb@suse.de>,
Mike Hommey <mh@glandium.org>, Taras Glek <tglek@mozilla.com>,
KOSAKI Motohiro <kosaki.motohiro@gmail.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Subject: Re: [RFC v5 0/8] Support volatile for anonymous range
Date: Thu, 3 Jan 2013 09:19:08 -0800 [thread overview]
Message-ID: <CAOMbAgLaFR+Et=F5+A7HPY16X-Y8VPm6mY_vE9XOJm8C-8OfPg@mail.gmail.com> (raw)
In-Reply-To: <1357187286-18759-1-git-send-email-minchan@kernel.org>
On Wed, Jan 2, 2013 at 8:27 PM, Minchan Kim <minchan@kernel.org> wrote:
> This is still RFC because we need more input from user-space
> people, more stress test, design discussion about interface/reclaim
Speaking as one of the authors of tcmalloc, I don't see any particular
need for this new system call for tcmalloc. We are fine using
madvise(MADV_DONTNEED) and don't notice any significant
performance issues caused by it. Background: we throttle how
quickly we release memory back to the system (1-10MB/s), so
we do not call madvise() very much, and we don't end up reusing
madvise-ed away pages at a fast rate. My guess is that we won't
see large enough application-level performance improvements to
cause us to change tcmalloc to use this system call.
> - What's different with madvise(DONTNEED)?
>
> System call semantic
>
> DONTNEED makes sure user always can see zero-fill pages after
> he calls madvise while mvolatile can see old data or encounter
> SIGBUS.
Do you need a new system call for this? Why not just a new flag to madvise
with weaker guarantees than zero-filling? All of the implementation changes
you point out below could be triggered from that flag.
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next prev parent reply other threads:[~2013-01-03 17:19 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-03 4:27 Minchan Kim
2013-01-03 4:27 ` [RFC 1/8] Introduce new system call mvolatile Minchan Kim
2013-01-03 18:35 ` Taras Glek
2013-01-04 4:25 ` Minchan Kim
2013-01-17 1:48 ` John Stultz
2013-01-18 5:30 ` Minchan Kim
2013-01-03 4:28 ` [RFC 2/8] Don't allow volatile attribute on THP and KSM Minchan Kim
2013-01-03 16:27 ` Dave Hansen
2013-01-04 2:51 ` Minchan Kim
2013-01-03 4:28 ` [RFC 3/8] bail out when the page is in VOLATILE vma Minchan Kim
2013-01-03 4:28 ` [RFC 4/8] add page_locked parameter in free_swap_and_cache Minchan Kim
2013-01-03 4:28 ` [RFC 5/8] Discard volatile page Minchan Kim
2013-01-03 4:28 ` [RFC 6/8] add PGVOLATILE vmstat count Minchan Kim
2013-01-03 4:28 ` [RFC 7/8] add volatile page discard hook to kswapd Minchan Kim
2013-01-03 4:28 ` [RFC 8/8] extend PGVOLATILE vmstat " Minchan Kim
2013-01-03 17:19 ` Sanjay Ghemawat [this message]
2013-01-04 5:15 ` [RFC v5 0/8] Support volatile for anonymous range Minchan Kim
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