From: Jeremy Allison <jra@samba.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Hellwig <hch@infradead.org>,
Jeremy Allison <jra@samba.org>, Milosz Tanski <milosz@adfin.com>,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-aio@kvack.org, Mel Gorman <mgorman@suse.de>,
Volker Lendecke <Volker.Lendecke@sernet.de>,
Tejun Heo <tj@kernel.org>, Jeff Moyer <jmoyer@redhat.com>,
Theodore Ts'o <tytso@mit.edu>, Al Viro <viro@zeniv.linux.org.uk>,
linux-api@vger.kernel.org,
Michael Kerrisk <mtk.manpages@gmail.com>,
linux-arch@vger.kernel.org, Dave Chinner <david@fromorbit.com>
Subject: Re: [PATCH v7 0/5] vfs: Non-blockling buffered fs read (page cache only)
Date: Mon, 30 Mar 2015 13:32:27 -0700 [thread overview]
Message-ID: <20150330203227.GA4987@samba2> (raw)
In-Reply-To: <20150330132625.52b1250527ca3dcda79e349e@linux-foundation.org>
On Mon, Mar 30, 2015 at 01:26:25PM -0700, Andrew Morton wrote:
>
> cons:
>
> d) fincore() is more expensive
>
> e) fincore() will very occasionally block
The above is the killer for Samba. If fincore
returns true but when we schedule the pread
we block, we're hosed.
Once we block, we're done serving clients on the main
thread until this returns. That can cause unpredictable
response times which can cause client timeouts.
A fincore+pread solution that blocks is simply unsafe
to use for us. We'll have to stay with the threadpool :-(.
> And I don't believe that e) will be a problem in the real world. It's
> a significant increase in worst-case latency and a negligible increase
> in average latency. I've asked at least three times for someone to
> explain why this is unacceptable and no explanation has been provided.
See above.
next prev parent reply other threads:[~2015-03-30 20:32 UTC|newest]
Thread overview: 108+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-16 18:27 [PATCH v7 0/5] vfs: Non-blockling buffered fs read (page cache only) Milosz Tanski
2015-03-16 18:27 ` [PATCH v7 1/5] vfs: Prepare for adding a new preadv/pwritev with user flags Milosz Tanski
2015-03-16 18:27 ` Milosz Tanski
2015-03-16 21:05 ` Andreas Dilger
2015-03-16 21:05 ` Andreas Dilger
2015-03-16 18:27 ` [PATCH v7 2/5] vfs: Define new syscalls preadv2,pwritev2 Milosz Tanski
2015-03-16 18:27 ` Milosz Tanski
2015-03-16 18:27 ` [PATCH v7 3/5] x86: wire up preadv2 and pwritev2 Milosz Tanski
2015-03-16 18:27 ` Milosz Tanski
2015-03-16 18:27 ` [PATCH v7 4/5] vfs: RWF_NONBLOCK flag for preadv2 Milosz Tanski
2015-03-16 18:27 ` Milosz Tanski
2015-03-16 18:27 ` [PATCH v7 5/5] xfs: add RWF_NONBLOCK support Milosz Tanski
2015-03-16 18:27 ` Milosz Tanski
2015-03-16 22:04 ` Dave Chinner
2015-03-16 22:04 ` Dave Chinner
2015-03-16 18:32 ` [PATCH] Add preadv2/pwritev2 documentation Milosz Tanski
2015-03-16 18:32 ` Milosz Tanski
2015-03-27 16:49 ` Andrew Morton
2015-03-27 16:49 ` Andrew Morton
[not found] ` <20150327094932.31b5c9fc.akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
2015-03-30 7:33 ` Christoph Hellwig
2015-03-30 7:33 ` Christoph Hellwig
2015-03-26 11:55 ` [PATCH v7 0/5] vfs: Non-blockling buffered fs read (page cache only) Christoph Hellwig
2015-03-26 11:55 ` Christoph Hellwig
2015-03-26 19:12 ` Milosz Tanski
2015-03-26 19:12 ` Milosz Tanski
2015-03-27 2:26 ` Milosz Tanski
2015-03-27 2:29 ` Milosz Tanski
2015-03-27 2:29 ` Milosz Tanski
[not found] ` <cover.1426528417.git.milosz-B5zB6C1i6pkAvxtiuMwx3w@public.gmane.org>
2015-03-16 18:34 ` [PATCH] fstests: generic test for preadv2 behavior on linux Milosz Tanski
2015-03-16 18:34 ` Milosz Tanski
2015-03-16 21:07 ` Andreas Dilger
2015-03-16 21:07 ` Andreas Dilger
2015-03-16 22:03 ` Milosz Tanski
2015-03-16 22:02 ` Dave Chinner
2015-03-16 22:02 ` Dave Chinner
2015-03-16 22:11 ` Milosz Tanski
2015-03-16 22:11 ` Milosz Tanski
[not found] ` <CANP1eJEj2buvwaU-jum=GROowY6DrysQ0NU+weXstn=83yVspQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2015-03-16 22:56 ` Dave Chinner
2015-03-16 22:56 ` Dave Chinner
2015-03-27 3:28 ` [PATCH v7 0/5] vfs: Non-blockling buffered fs read (page cache only) Andrew Morton
2015-03-27 3:28 ` Andrew Morton
2015-03-27 5:41 ` Volker Lendecke
2015-03-27 5:41 ` Volker Lendecke
[not found] ` <E1YbN1J-0084qO-3s-dqLtpHMqGvUyWpdLl23E4A@public.gmane.org>
2015-03-27 6:08 ` Andrew Morton
2015-03-27 6:08 ` Andrew Morton
[not found] ` <20150326230833.4ccfaebb.akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
2015-03-27 8:02 ` Volker Lendecke
2015-03-27 8:02 ` Volker Lendecke
2015-03-27 8:12 ` Christoph Hellwig
2015-03-27 8:12 ` Christoph Hellwig
2015-03-27 8:18 ` Christoph Hellwig
2015-03-27 8:18 ` Christoph Hellwig
[not found] ` <20150327081822.GA28669-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2015-03-27 8:35 ` Andrew Morton
2015-03-27 8:35 ` Andrew Morton
2015-03-27 8:48 ` Christoph Hellwig
2015-03-27 8:48 ` Christoph Hellwig
[not found] ` <20150327084833.GA7689-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2015-03-27 9:01 ` Andrew Morton
2015-03-27 9:01 ` Andrew Morton
2015-03-27 9:44 ` Volker Lendecke
2015-03-27 9:44 ` Volker Lendecke
2015-03-27 15:58 ` Jeremy Allison
2015-03-27 15:58 ` Jeremy Allison
2015-03-27 16:30 ` Andrew Morton
2015-03-27 16:30 ` Andrew Morton
2015-03-27 16:39 ` Jeremy Allison
2015-03-27 16:39 ` Jeremy Allison
2015-03-27 16:39 ` Andrew Morton
2015-03-27 16:39 ` Andrew Morton
2015-03-27 16:45 ` Milosz Tanski
2015-03-27 16:45 ` Milosz Tanski
2015-03-31 1:27 ` Milosz Tanski
2015-03-27 16:38 ` Milosz Tanski
2015-03-27 16:38 ` Milosz Tanski
2015-03-30 7:36 ` Christoph Hellwig
2015-03-30 7:36 ` Christoph Hellwig
[not found] ` <20150330073604.GB22229-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2015-03-30 17:19 ` Jeremy Allison
2015-03-30 17:19 ` Jeremy Allison
2015-03-30 22:51 ` Milosz Tanski
2015-03-30 20:26 ` Andrew Morton
2015-03-30 20:26 ` Andrew Morton
2015-03-30 20:32 ` Jeremy Allison [this message]
2015-03-30 20:37 ` Andrew Morton
2015-03-30 20:49 ` Jeremy Allison
2015-03-30 20:49 ` Jeremy Allison
2015-03-30 21:33 ` Andrew Morton
2015-03-30 22:35 ` Milosz Tanski
2015-03-30 22:35 ` Milosz Tanski
2015-03-30 22:49 ` Milosz Tanski
2015-03-30 22:57 ` Andrew Morton
[not found] ` <20150330155700.92f4c8a0bf13418aaf01ae04-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
2015-03-30 23:06 ` Milosz Tanski
2015-03-30 23:06 ` Milosz Tanski
2015-03-30 23:25 ` Milosz Tanski
2015-03-30 23:25 ` Milosz Tanski
2015-04-04 3:42 ` Andrew Morton
2015-04-04 3:42 ` Andrew Morton
[not found] ` <20150403204209.75405f37.akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
2015-04-06 3:53 ` Milosz Tanski
2015-04-06 3:53 ` Milosz Tanski
2015-03-30 23:09 ` Milosz Tanski
2015-03-30 23:09 ` Milosz Tanski
2015-03-27 15:21 ` Milosz Tanski
2015-03-27 15:21 ` Milosz Tanski
2015-03-27 17:04 ` Andrew Morton
2015-03-27 17:04 ` Andrew Morton
2015-03-30 7:40 ` Christoph Hellwig
2015-03-30 7:40 ` Christoph Hellwig
2015-03-30 18:54 ` Andrew Morton
2015-03-30 22:40 ` Milosz Tanski
[not found] ` <CANP1eJH4BcZ0vgZ6pZdKOd4orEzfKUqjpKXb3m=WMy0mbK+PFA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2015-03-30 22:50 ` Andrew Morton
2015-03-30 22:50 ` Andrew Morton
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