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From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Tejun Heo <htejun@gmail.com>
Cc: Jeff Garzik <jgarzik@pobox.com>,
	linux-ide@vger.kernel.org, albertcc@tw.ibm.com, mlord@pobox.com,
	lkosewsk@gmail.com, luben_tuikov@adaptec.com,
	Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>,
	Jens Axboe <axboe@suse.de>
Subject: Re: [SUMMARY] libata EH
Date: Sat, 20 Aug 2005 21:02:48 +0100	[thread overview]
Message-ID: <1124568170.14518.13.camel@localhost.localdomain> (raw)
In-Reply-To: <430768E2.60808@gmail.com>

On Sul, 2005-08-21 at 02:31 +0900, Tejun Heo wrote:
>   My preference is toward unifying into single path as long as 
> performance penalty is acceptable for the sake of simplicity.

I don't think it is a big issue for ATA. The drive tends to take 10-15
seconds before it goes and whines at us, and it is hopefully not a fast
path.

> >>     * SCSI EH entrance is not synchronized with polling tasks.
> > 
> > 
> > Yes, this definitely needs fixing.
> > 
> > Luckily the polling task is very rarely used, by normal users.

The old IDE has this bug on reset paths too - and people do eventually
hit it.

> > - DMA errors should be handled by hueristics:  If more than $N (3?) DMA 
> > errors happen in 15 minutes,
> > * decrease SATA PHY speed.  if speed cannot be decreased,
> > * decrease UDMA xfer speed.  if at UDMA0, switch to PIO4
> > * decrease PIO xfer speed.  if at PIO3, complain, but continue

Remember this means issuing a command to the drive before re-issuing the
failed command. The old IDE also has serious problems with this as it
ends up trying to issue a polling command from an IRQ racing its own
timeout code. One good reason for the EH approach scsi takes of
quiescing first and running in task context.



  reply	other threads:[~2005-08-20 19:52 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2005-08-20  2:33 [SUMMARY] libata EH Tejun Heo
2005-08-20  4:48 ` Jeff Garzik
2005-08-20 17:31   ` Tejun Heo
2005-08-20 20:02     ` Alan Cox [this message]
2005-08-21  4:09     ` Jeff Garzik

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