From: Jens Axboe <jens.axboe@oracle.com>
To: linux-btrace@vger.kernel.org
Subject: Re: BLK_TA_ISSUE
Date: Thu, 12 Apr 2007 11:29:20 +0000 [thread overview]
Message-ID: <20070412112920.GB19066@kernel.dk> (raw)
In-Reply-To: <1176341579.3409.2.camel@localhost.localdomain>
On Wed, Apr 11 2007, Ming Zhang wrote:
> Hi All
>
> For this ISSUE event, currently it is in elv_next_request(), any idea
> why it is not in elv_dequeue_request() which is where the request marked
> as on-the-fly and send to lower level?
elv_next_request() is the driver hand-off point, so should be pretty
close to the issue time unless the request gets requeued due to some
busy condition (which will also be logged). elv_dequeue_request() may
happen much later, some drivers do it right before calling the io
completion handler - IDE does this - since it leaves the request on the
queue list for the duration of the operation. So moving the ISSUE event
to elv_dequeue_request() would not be correct.
--
Jens Axboe
next prev parent reply other threads:[~2007-04-12 11:29 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-04-12 1:32 BLK_TA_ISSUE Ming Zhang
2007-04-12 11:29 ` Jens Axboe [this message]
2007-04-12 13:18 ` BLK_TA_ISSUE Ming Zhang
2007-04-12 21:16 ` BLK_TA_ISSUE Jens Axboe
2007-04-12 21:22 ` BLK_TA_ISSUE Ming Zhang
2007-04-13 5:30 ` BLK_TA_ISSUE Jens Axboe
2007-04-13 13:18 ` BLK_TA_ISSUE Ming Zhang
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