From: Linus Torvalds <torvalds@transmeta.com>
To: James Bottomley <James.Bottomley@SteelEye.com>
Cc: Jens Axboe <axboe@suse.de>, Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: [BK PATCHES] add ata scsi driver
Date: Mon, 26 May 2003 13:27:17 -0700 (PDT) [thread overview]
Message-ID: <Pine.LNX.4.44.0305261317520.12186-100000@home.transmeta.com> (raw)
In-Reply-To: <1053976644.2298.194.camel@mulgrave>
On 26 May 2003, James Bottomley wrote:
>
> On Mon, 2003-05-26 at 15:07, Jens Axboe wrote:
> > Alright, so what do you need? Start out with X tags, shrink to Y (based
> > on repeated queue full conditions)? Anything else?
>
> Actually, it's easier than that: just an API to alter the number of tags
> in the block layer (really only the size of your internal hash table).
> The actual heuristics of when to alter the queue depth is the province
> of the individual drivers (although Doug Ledford was going to come up
> with a generic implementation).
Talking about tagged queueing - does the SCSI layer still remove the
request from the request list when it starts executing it?
At least historically that's a major mistake, and generates a crappy
elevator, because it removes information from the block layer about where
the disk is (or is going to be).
I know Andrew thinks that SCSI tagged queuing is a bunch of crap, and he
has the latency numbers to prove it. He blames the SCSI disks themselves,
but I think it might be the fact that SCSI makes it impossible to make a
fair queuing algorithm for higher levels by hiding information.
Has anybody looked at just removing the request at command _completion_
time instead? That's what IDE does, and it's the _right_ thing to do.
I'd hate for SATA to pick up these kinds of mistakes from the SCSI layer.
Linus
next prev parent reply other threads:[~2003-05-26 20:14 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-05-26 18:12 [BK PATCHES] add ata scsi driver James Bottomley
2003-05-26 18:18 ` Jens Axboe
2003-05-26 18:47 ` James Bottomley
2003-05-26 19:07 ` Jens Axboe
2003-05-26 19:17 ` James Bottomley
2003-05-26 19:33 ` Jens Axboe
2003-05-27 12:39 ` Jens Axboe
2003-05-27 14:26 ` James Bottomley
2003-05-27 17:16 ` Jens Axboe
2003-05-27 18:09 ` James Bottomley
2003-05-27 18:21 ` Jens Axboe
2003-05-27 18:30 ` James Bottomley
2003-05-26 20:27 ` Linus Torvalds [this message]
2003-05-26 20:36 ` James Bottomley
2003-05-26 20:45 ` Linus Torvalds
2003-05-26 20:51 ` Jens Axboe
2003-05-26 20:56 ` James Bottomley
2003-05-26 20:38 ` Jens Axboe
2003-05-26 20:49 ` Linus Torvalds
2003-05-26 20:57 ` Jens Axboe
2003-05-26 21:34 ` Linus Torvalds
2003-05-26 23:58 ` Nick Piggin
2003-05-27 0:09 ` Linus Torvalds
2003-05-27 0:49 ` Nick Piggin
2003-05-27 0:16 ` Alan Cox
2003-05-27 6:54 ` Jens Axboe
2003-05-27 14:20 ` James Bottomley
2003-05-27 14:36 ` Linus Torvalds
2003-05-27 14:59 ` James Bottomley
2003-05-27 15:21 ` Jeff Garzik
2003-05-27 15:38 ` James Bottomley
2003-05-27 15:50 ` Jeff Garzik
2003-05-27 16:00 ` James Bottomley
2003-05-27 16:16 ` Jeff Garzik
2003-05-28 9:35 ` Christoph Hellwig
2003-05-28 10:50 ` Lincoln Dale
2003-05-27 19:43 ` Jens Axboe
-- strict thread matches above, loose matches on Subject: below --
2003-05-26 4:58 Jeff Garzik
2003-05-26 5:15 ` Linus Torvalds
2003-05-26 5:30 ` Jeff Garzik
2003-05-26 5:36 ` Jeff Garzik
2003-05-26 5:42 ` Linus Torvalds
2003-05-26 6:01 ` Jeff Garzik
2003-05-26 16:56 ` Linus Torvalds
2003-05-26 17:47 ` Jeff Garzik
2003-05-26 20:09 ` Linus Torvalds
2003-05-27 0:29 ` Alan Cox
2003-05-27 6:07 ` Jeff Garzik
2003-05-27 6:30 ` Linus Torvalds
2003-05-27 6:51 ` Linus Torvalds
2003-05-27 7:29 ` Jeff Garzik
2003-05-26 5:40 ` Linus Torvalds
2003-05-26 5:53 ` Jeff Garzik
2003-05-26 6:21 ` Jeff Garzik
2003-05-26 16:57 ` Linus Torvalds
2003-05-26 17:24 ` Jens Axboe
2003-05-26 17:54 ` Jeff Garzik
2003-05-26 17:59 ` Jeff Garzik
2003-05-26 18:11 ` Jens Axboe
2003-05-27 0:22 ` Alan Cox
2003-05-27 4:15 ` Linus Torvalds
2003-05-26 10:32 ` Bartlomiej Zolnierkiewicz
2003-05-26 11:13 ` Jeff Garzik
2003-05-26 11:37 ` Bartlomiej Zolnierkiewicz
2003-05-26 5:59 ` Benjamin Herrenschmidt
2003-05-26 6:03 ` Jeff Garzik
2003-06-02 9:46 ` Andre Hedrick
2003-06-02 13:56 ` Alan Cox
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