Date: Fri, 8 Apr 2005 11:45:58 +0200
From: Jens Axboe <axboe@suse.de>
To: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com>, linux-kernel@vger.kernel.org
Subject: Re: [patch] use cheaper elv_queue_empty when unplug a device
Message-ID: <20050408094557.GG22988@suse.de>
References: <200503290253.j2T2rqg25691@unix-os.sc.intel.com> <20050329080646.GE16636@suse.de> <42491DBE.6020303@yahoo.com.au> <20050329092819.GK16636@suse.de> <424928A1.8060400@yahoo.com.au> <4249F98D.9040706@yahoo.com.au>
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On Wed, Mar 30 2005, Nick Piggin wrote:
> Nick Piggin wrote:
> >Jens Axboe wrote:
> >
> >>Looks good, I've been toying with something very similar for a long time
> >>myself.
> >>
> >
> >Here is another thing I just noticed that should further reduce the
> >locking by at least 1, sometimes 2 lock/unlock pairs per request.
> >At the cost of uglifying the code somewhat. Although it is pretty
> >nicely contained, so Jens you might consider it acceptable as is,
> >or we could investigate how to make it nicer if Kenneth reports some
> >improvement.
> >
> >Note, this isn't runtime tested - it could easily have a bug.
> >
> 
> OK - I have booted this on a 4-way SMP with SCSI disks, and done
> some IO tests, and no hangs.
> 
> So Kenneth if you could look into this one as well, to see if
> it is worthwhile, that would be great.

For that to work, you have to change the get_io_context() allocation to
be GFP_ATOMIC.

-- 
Jens Axboe

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