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From: Jeff Garzik <jeff@garzik.org>
To: Ed Lin <ed.lin@promise.com>
Cc: Jens Axboe <jens.axboe@oracle.com>,
	David Somayajulu <david.somayajulu@qlogic.com>,
	Michael Reed <mdr@sgi.com>,
	linux-scsi <linux-scsi@vger.kernel.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	"james.Bottomley" <james.Bottomley@SteelEye.com>,
	Promise_Linux <Promise_Linux@promise.com>
Subject: Re: [patch] scsi: use lock per host instead of per device for shared queue tag host
Date: Thu, 25 Jan 2007 20:21:01 -0500	[thread overview]
Message-ID: <45B9577D.9000302@garzik.org> (raw)
In-Reply-To: <B70A50D07063384EB9BCE3330D18414F02F5B011@nonameb.ptu.promise.com>

Ed Lin wrote:
> There may possibly be some other errors. So we need a lock here.
> I think the simple but reliable way to do it is just to replace
> queue lock with a host lock. James pointed out that there may be
> performance slow down when many devices are accessed at the
> same time. But I think the major part is still on the hardware,
> and a host lock is the price these kind of controllers must pay.


I agree.

Further, a host lock is (a) common across many controllers, to protect 
host-wide resources and (b) only limits us when the controller is 
CPU-limited, a very rare scenario.

	Jeff



  reply	other threads:[~2007-01-26  1:21 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-01-26  1:15 Ed Lin
2007-01-26  1:21 ` Jeff Garzik [this message]
  -- strict thread matches above, loose matches on Subject: below --
2007-01-25  3:14 Ed Lin
2007-01-25 15:34 ` Jens Axboe
2007-01-25 15:47   ` Jens Axboe
2007-01-24 23:33 Ed Lin
2007-01-25  1:02 ` David Somayajulu
2007-01-24  0:53 Ed Lin
2007-01-24 15:59 ` Michael Reed
2007-01-24 16:59 ` James Bottomley

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