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From: John Stultz <john.stultz@linaro.org>
To: Dave Chinner <david@fromorbit.com>
Cc: linux-kernel@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	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>
Subject: Re: [PATCH 2/2] [RFC] fadvise: Add _VOLATILE,_ISVOLATILE, and _NONVOLATILE flags
Date: Tue, 14 Feb 2012 16:29:10 -0800	[thread overview]
Message-ID: <1329265750.2340.17.camel@work-vm> (raw)
In-Reply-To: <20120214235106.GL7479@dastard>

On Wed, 2012-02-15 at 10:51 +1100, Dave Chinner wrote:
> Given that it is a single state bit per page (volatile/non volatile)
> you could just use a radix tree tag for keeping the state. Changing
> the state isn't a performance critical operation, and tagging large
> ranges isn't that expensive (e.g. we do that in the writeback code),
> so I'm not sure the overhead of a separate tree is necessary here....

Hrm. I'll look into this.

> That doesn't help with the reclaim side of things, but I would have
> thought that such functioanlity would be better integrated into the
> VM page cache/lru scanning code than adding a shrinker to shrink the
> page cache additionally on top of what the VM has already done
> before calling the shrinkers. I'm not sure what is best here,
> though...

Yea. My previous version did eviction from shmem_writepage(), I believe
much as you suggest here, but the concern with that is that you could
have a larger volatile range that was for the most part recently in use,
but one idle page causes the entire thing to be evicted first. Using
least-recently-marked-volatile order seems more natural for the use case
(although Dimitry and others have already pointed out that the
inheritance from the coalescing of neighboring ranges results in a
similar issue).

But I'm open to other ideas and arguments.

Thanks again for the feedback!
-john


  reply	other threads:[~2012-02-15  0:29 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-02-10  0:16 [PATCH 1/2] [RFC] Range tree implementation John Stultz
2012-02-10  0:16 ` [PATCH 2/2] [RFC] fadvise: Add _VOLATILE,_ISVOLATILE, and _NONVOLATILE flags John Stultz
     [not found]   ` <CAO6Zf6B6nGqsz5zpT3ixbO-+JWxMsScABasnwo-CVHuMKPqpLQ@mail.gmail.com>
2012-02-12 12:54     ` Fwd: " Dmitry Adamushko
2012-02-17  3:43     ` John Stultz
2012-02-17  5:24       ` John Stultz
2012-02-12 14:08   ` Dmitry Adamushko
2012-02-17  3:49     ` John Stultz
2012-02-14  5:16   ` Dave Chinner
2012-02-14  5:55     ` John Stultz
2012-02-14 23:51       ` Dave Chinner
2012-02-15  0:29         ` John Stultz [this message]
2012-02-15  1:37           ` NeilBrown
2012-02-17  4:45             ` Dave Chinner
2012-02-17  5:27               ` NeilBrown
2012-02-17  5:38               ` John Stultz
2012-02-17  5:21             ` John Stultz
2012-02-20  7:34               ` NeilBrown
2012-02-20 23:25                 ` Dave Hansen
  -- strict thread matches above, loose matches on Subject: below --
2012-03-16 22:51 [PATCH 0/2] [RFC] Volatile ranges (v4) John Stultz
2012-03-16 22:51 ` [PATCH 2/2] [RFC] fadvise: Add _VOLATILE,_ISVOLATILE, and _NONVOLATILE flags John Stultz
2012-03-17 16:21   ` Dmitry Adamushko
2012-03-18  9:13     ` Dmitry Adamushko
2012-03-20  0:18     ` John Stultz
2012-03-21  4:15 [PATCH 0/2] [RFC] fadivse volatile & range tree (v5) John Stultz
2012-03-21  4:15 ` [PATCH 2/2] [RFC] fadvise: Add _VOLATILE,_ISVOLATILE, and _NONVOLATILE flags John Stultz
2012-04-07  0:08 [PATCH 0/2] [RFC] Volatile Ranges (v6) John Stultz
2012-04-07  0:08 ` [PATCH 2/2] [RFC] fadvise: Add _VOLATILE,_ISVOLATILE, and _NONVOLATILE flags John Stultz
2012-04-14  1:07 [PATCH 0/2][RFC] Volatile Ranges (v7) John Stultz
2012-04-14  1:08 ` [PATCH 2/2] [RFC] fadvise: Add _VOLATILE,_ISVOLATILE, and _NONVOLATILE flags John Stultz

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