linux-kernel - Re: [PATCH 4/7] libata: use lazy workqueues for the pio task

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Message-ID: <4A92C55F.6080506@garzik.org>
Date:	Mon, 24 Aug 2009 12:52:47 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	John Stoffel <john@...ffel.org>
CC:	Jens Axboe <jens.axboe@...cle.com>, linux-kernel@...r.kernel.org,
	benh@...nel.crashing.org, htejun@...il.com, bzolnier@...il.com,
	alan@...rguk.ukuu.org.uk, akpm@...ux-foundation.org
Subject: Re: [PATCH 4/7] libata: use lazy workqueues for the pio task

On 08/24/2009 12:45 PM, John Stoffel wrote:
>>>>>> "Jeff" == Jeff Garzik<jeff@...zik.org>  writes:
> Jeff>  No objections to the code, operationally...
>
> Jeff>  But it is disappointing that the "1 thread on UP" problem is not
> Jeff>  solved while changing this libata area.  Is there no way to
> Jeff>  specify a minimum lazy-thread count?
>
> Jeff>  A key problem continues to be tying to the number of CPUs, which
> Jeff>  is quite inappropriate for libata.
>
> So should the minimum number be the NumATADisks on the system?  Actual
> or potential?  I've got a system with dual CPUs and two IDE disk, two
> SATA disks and two SCSI disks, plus two SCSI Tape drives.  All on
> seperate controllers... how would that work?

Technically speaking, the maximum is the number of PIO-polling devices.

Theoretically this can change with hotplugging, but that is _very_ rare 
-- mainly PATA+media bay situations, or bridged SATA with an ancient 
PATA device.

	Jeff




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