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

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Date:	Wed, 14 Aug 2013 21:41:14 +0000
From:	"Miller, Mike (OS Dev)" <Mike.Miller@...com>
To:	James Bottomley <James.Bottomley@...senPartnership.com>,
	"mikem@...mper.usa.hp.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" <thenzl@...hat.com>,
	"bubrown@...hat.com" <bubrown@...hat.com>,
	"scameron@...rdog.cce.hp.com" <scameron@...rdog.cce.hp.com>
Subject: RE: [PATCH 1/1] cciss: set max scatter gather entries to 32 on P600



-----Original Message-----
From: James Bottomley [mailto:James.Bottomley@...senPartnership.com] 
Sent: Wednesday, August 14, 2013 4:27 PM
To: Miller, Mike (OS Dev); mikem@...mper.usa.hp.com
Cc: Andrew Morton; Jens Axboe; LKML-scsi; LKML; 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

The patch origin is unknown. I got it from Tomas and Bud who think it may have originated from HP. I cleaned it up, compile tested it, and sent it on. I'll review my procedures for future patches.

-- mikem


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