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From: "Ted Ts'o" <tytso@mit.edu>
To: Dave Chinner <david@fromorbit.com>
Cc: Andi Kleen <andi@firstfloor.org>,
	Christoph Hellwig <hch@infradead.org>,
	Daniel Ehrenberg <dehrenberg@google.com>,
	linux-kernel@vger.kernel.org
Subject: Re: Approaches to making io_submit not block
Date: Fri, 2 Sep 2011 09:08:35 -0400	[thread overview]
Message-ID: <20110902130835.GB4110@thunk.org> (raw)
In-Reply-To: <20110901065415.GP32358@dastard>

On Thu, Sep 01, 2011 at 04:54:15PM +1000, Dave Chinner wrote:
> Apples to oranges - there's orders of magnitude of difference in the
> number of operations that the different stacks do. Allocation in XFS
> when it does not block can still take milliseconds of CPU time; in
> comparison, the networking stack is expected to process thousands of
> packets in that same time frame.  IOWs, the scale of processing per
> item of work is -vastly- different - that's why working in process
> context matters a great deal to the networking stack but not to
> allocation in XFS.

That may be true for hard drives, but PCIe attached flash can support
millions of IOP's per second --- i.e., at least hundreds of IOP's in
milliseconds.  Yes, these devices are expensive, but so are the
thousand-disk RAID arrays that some people attach via XFS.  :-)

There are people in the ext4 development community interested in
looking at such devices.  We've made some improvements, we (and by
this I mean the whole kernel) are a long, long way from supporting
such beasts properly....

							- Ted

  reply	other threads:[~2011-09-02 13:08 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
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 [this message]
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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