linux-kernel - Re: [PATCH 1/1] cciss: set max scatter gather entries to 32 on P600

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Message-ID: <1376515627.2028.41.camel@dabdike.int.hansenpartnership.com>
Date:	Wed, 14 Aug 2013 14:27:07 -0700
From:	James Bottomley <James.Bottomley@...senPartnership.com>
To:	mike.miller@...com, mikem@...mper.usa.hp.com
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Jens Axboe <axboe@...nel.dk>,
	LKML-scsi <linux-scsi@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>, thenzl@...hat.com,
	bubrown@...hat.com, scameron@...rdog.cce.hp.com
Subject: Re: [PATCH 1/1] cciss: set max scatter gather entries to 32 on P600

On Wed, 2013-08-14 at 15:52 -0500, Mike Miller wrote:
> Patch 1/1
> 
> From: Mike Miller <mike.miller@...com>
> 
> At one time we used to set the maximum number of scatter gather elements on 
> all Smart Array controllers to 32. At some point in time the firmware began 
> to write the "appropriate" value for each controller into the config table. 
> The cciss driver would then read that and set h->maxsgentries.
> 
>         h->maxsgentries = readl(&(h->cfgtable->MaxSGElements);
> 
> On the P600 that value is 544. Under some workloads a significant 
> performance reduction may result. This patch forces the P600 to use only 32 
> scatter gather elements. Other controllers are not affected.
> 
> Signed-off-by: Mike Miller <mike.miller@...com>
> Signed-off-by: Dwight (Bud) Brown <bubrown@...hat.com>
> Signed-off-by: Tomas Henzl <thenzl@...hat.com>
> Acked-by: Stephen M. Cameron <steve.cameron@...com>

I don't quite understand the signoff chain on this patch.  For a one
line patch, are you saying it has three authors?

James


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