From: Bart Van Assche <bvanassche@acm.org>
To: scameron@beardog.cce.hp.com
Cc: Christoph Hellwig <hch@infradead.org>,
linux-scsi@vger.kernel.org, stephenmcameron@gmail.com,
dab@hp.com
Subject: Re: SCSI mid layer and high IOPS capable devices
Date: Fri, 14 Dec 2012 17:15:37 +0100 [thread overview]
Message-ID: <50CB50A9.1050202@acm.org> (raw)
In-Reply-To: <20121214164421.GQ20898@beardog.cce.hp.com>
On 12/14/12 17:44, scameron@beardog.cce.hp.com wrote:
> I expect the flash devices re-order requests as well, simply because
> to feed requests to the things at a sufficient rate, you have to pump
> requests into them concurrently on multiple hardware queues -- a single
> cpu jamming requests into them as fast as it can is still not fast enough
> to keep them busy. Consequently, they *can't* care about ordering, as the
> relative order requests on different hardware queues are submitted into them
> is not even really controlled, so the OS *can't* count on concurrent requests
> not to be essentially "re-ordered", just because of the nature of the way
> requests get into the device.
Why should a flash device have to reorder write requests ? These devices
typically use a log-structured file system internally.
Bart.
next prev parent reply other threads:[~2012-12-14 16:15 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-11 0:00 SCSI mid layer and high IOPS capable devices scameron
2012-12-11 8:21 ` Bart Van Assche
2012-12-11 22:46 ` scameron
2012-12-13 11:40 ` Bart Van Assche
2012-12-13 18:03 ` scameron
2012-12-13 17:18 ` Bart Van Assche
2012-12-13 15:22 ` Bart Van Assche
2012-12-13 17:25 ` scameron
2012-12-13 16:47 ` Bart Van Assche
2012-12-13 16:49 ` Christoph Hellwig
2012-12-14 9:44 ` Bart Van Assche
2012-12-14 16:44 ` scameron
2012-12-14 16:15 ` Bart Van Assche [this message]
2012-12-14 19:55 ` scameron
2012-12-14 19:28 ` Bart Van Assche
2012-12-14 21:06 ` scameron
2012-12-15 9:40 ` Bart Van Assche
2012-12-19 14:23 ` Christoph Hellwig
2012-12-13 21:20 ` scameron
2012-12-14 0:22 ` Jack Wang
[not found] ` <CADzpL0TMT31yka98Zv0=53N4=pDZOc9+gacnvDWMbj+iZg4H5w@mail.gmail.com>
[not found] ` <006301cdd99c$35099b40$9f1cd1c0$@com>
[not found] ` <CADzpL0S5cfCRQftrxHij8KOjKj55psSJedmXLBQz1uQm_SC30A@mail.gmail.com>
2012-12-14 4:59 ` Jack Wang
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