From: Mike Christie <michaelc@cs.wisc.edu>
To: Matthew Wilcox <matthew@wil.cx>
Cc: Andrew Morton <akpm@osdl.org>, Martin Peschke <mp3@de.ibm.com>,
linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org
Subject: Re: [Patch] SCSI I/O statistics
Date: Tue, 26 Sep 2006 16:45:54 -0500 [thread overview]
Message-ID: <45199F92.106@cs.wisc.edu> (raw)
In-Reply-To: <20060926182347.GH5017@parisc-linux.org>
Matthew Wilcox wrote:
> On Tue, Sep 26, 2006 at 10:39:30AM -0700, Andrew Morton wrote:
>> - Should it have been done at the block layer rather than at the scsi layer?
>
> This was already mentioned when he sent it to linux-scsi a few days ago.
> There are scsi commands which bypass the block layer, such as SG_IO, and
I do not think any command completely bypasses the block layer now.
SG_IO, tape, sd and scanning insertion go through blk_execute_rq_nowait
for insertion. For completion they go through blk_complete_request +
end_that_request_first/last in the normal path and blk_complete_request
+ blk_requeue_request in the retry path.
> block layer stats can make an extremely busy disc look not busy.
> -
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next prev parent reply other threads:[~2006-09-26 21:46 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-09-26 15:56 [Patch] SCSI I/O statistics Martin Peschke
2006-09-26 17:39 ` Andrew Morton
2006-09-26 18:23 ` Matthew Wilcox
2006-09-26 21:45 ` Mike Christie [this message]
2006-09-27 14:35 ` Martin Peschke
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