From: Andi Kleen <andi@firstfloor.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: Daniel Ehrenberg <dehrenberg@google.com>, linux-kernel@vger.kernel.org
Subject: Re: Approaches to making io_submit not block
Date: Wed, 31 Aug 2011 10:08:50 -0700 [thread overview]
Message-ID: <m2pqjlo6e5.fsf@firstfloor.org> (raw)
In-Reply-To: <20110831052627.GA5338@infradead.org> (Christoph Hellwig's message of "Wed, 31 Aug 2011 01:26:27 -0400")
Christoph Hellwig <hch@infradead.org> writes:
>
> I'll get it polished up and send it out for RFC once Dave sends out
> the updated allocation workqueue patch. With this he moves all
> allocator calls in XFS into a workqueue. My direct I/O patch uses that
> fact to use that workqueue for the allocator call
Is that really a good direction? The problem when you push operations
from multiple threads all into a single resource (per cpu workqueue)
is that the CPU scheduler loses control over that because they
are all mixed up.
So if one guy submits a lot and another very little the "a lot" guy
can overwhelm the queue for the very little guy.
We also have similar problems with the IO schedulers, which also
rely on process context to make fairness decisions. If you remove
the process context they do badly.
-Andi
--
ak@linux.intel.com -- Speaking for myself only
next prev parent reply other threads:[~2011-08-31 17:08 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-29 17:33 Approaches to making io_submit not block Daniel Ehrenberg
2011-08-30 5:32 ` Christoph Hellwig
2011-08-30 21:51 ` Daniel Ehrenberg
2011-08-31 5:26 ` Christoph Hellwig
2011-08-31 17:08 ` Andi Kleen [this message]
2011-08-31 21:00 ` Daniel Ehrenberg
2011-08-31 21:15 ` Andi Kleen
2011-09-01 4:18 ` Dave Chinner
2011-09-01 4:39 ` Andi Kleen
2011-09-01 6:54 ` Dave Chinner
2011-09-02 13:08 ` Ted Ts'o
2011-09-02 13:10 ` Christoph Hellwig
2011-09-01 3:39 ` Dave Chinner
2011-09-01 4:20 ` Christoph Hellwig
2011-08-30 7:02 ` Andi Kleen
[not found] ` <CAAK6Zt0Sh1GdEOb-tNf2FGXJs=e1Jbcqew13R_GdTqrv6vW97w@mail.gmail.com>
[not found] ` <x49k49uk2ox.fsf@segfault.boston.devel.redhat.com>
[not found] ` <4E5D5817.6040704@kernel.dk>
2011-08-30 22:19 ` Daniel Ehrenberg
2011-08-30 22:32 ` Jens Axboe
2011-08-30 22:41 ` Andrew Morton
2011-08-30 22:45 ` Daniel Ehrenberg
2011-08-30 22:54 ` Andrew Morton
2011-08-30 23:03 ` Jeremy Allison
2011-08-30 23:11 ` Andrew Morton
2011-08-31 11:04 ` Ulrich Drepper
2011-08-31 16:59 ` Jeremy Allison
2011-09-01 11:14 ` Ulrich Drepper
2011-09-01 15:58 ` Jeremy Allison
2011-09-01 16:04 ` Christoph Hellwig
2011-09-01 16:15 ` Jeremy Allison
2011-09-01 16:23 ` Christoph Hellwig
2011-09-01 16:31 ` Jeremy Allison
2011-09-01 16:34 ` Christoph Hellwig
2011-09-01 16:34 ` Jeremy Allison
2011-09-01 16:45 ` Christoph Hellwig
2011-09-01 16:57 ` Jeremy Allison
2011-08-31 5:34 ` Christoph Hellwig
2011-08-31 6:04 ` guy keren
2011-08-31 23:16 ` Daniel Ehrenberg
2011-08-31 23:48 ` guy keren
2011-08-31 23:59 ` Daniel Ehrenberg
2011-08-31 15:45 ` Gleb Natapov
2011-08-31 16:02 ` Avi Kivity
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