From: Bart Van Assche <bvanassche@acm.org>
To: scameron@beardog.cce.hp.com
Cc: linux-scsi@vger.kernel.org, stephenmcameron@gmail.com, dab@hp.com
Subject: Re: SCSI mid layer and high IOPS capable devices
Date: Thu, 13 Dec 2012 16:22:33 +0100 [thread overview]
Message-ID: <50C9F2B9.4050500@acm.org> (raw)
In-Reply-To: <20121211000013.GI23107@beardog.cce.hp.com>
On 12/11/12 01:00, scameron@beardog.cce.hp.com wrote:
> The driver, like nvme, has a submit and reply queue per cpu.
This is interesting. If my interpretation of the POSIX spec is correct
then aio_write() allows to queue overlapping writes and all writes
submitted by the same thread have to be performed in the order they were
submitted by that thread. What if a thread submits a first write via
aio_write(), gets rescheduled on another CPU and submits a second
overlapping write also via aio_write() ? If a block driver uses one
queue per CPU, does that mean that such writes that were issued in order
can be executed in a different order by the driver and/or hardware than
the order in which the writes were submitted ?
See also the aio_write() man page, The Open Group Base Specifications
Issue 7, IEEE Std 1003.1-2008
(http://pubs.opengroup.org/onlinepubs/9699919799/functions/aio_write.html).
Bart.
next prev parent reply other threads:[~2012-12-13 15:22 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 [this message]
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
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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