linux-kernel - Re: [PATCH v3] storvsc: use small sg

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Message-ID: <20160609220120.GA28607@aepfle.de>
Date:	Fri, 10 Jun 2016 00:01:20 +0200
From:	Olaf Hering <olaf@...fle.de>
To:	James Bottomley <jejb@...ux.vnet.ibm.com>
Cc:	"K. Y. Srinivasan" <kys@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	devel@...uxdriverproject.org, linux-kernel@...r.kernel.org,
	linux-scsi@...r.kernel.org
Subject: Re: [PATCH v3] storvsc: use small sg_tablesize on x86

On Thu, Jun 09, James Bottomley wrote:

> On Thu, 2016-06-09 at 18:25 +0200, Olaf Hering wrote:
> > Reducing the sg_tablesize allows booting of 32bit kernels in VMs,
> > after
> > commit be0cf6ca301c61458dc4aa1a37acf4f58d2ed3d6 ("scsi: storvsc: Set
> > the
> > tablesize based on the information given by the host")
> > 
> > [    5.567138] hv_storvsc vmbus_1: adjusting sg_tablesize 0x800 -> 
> > 0x20
> 
> Are you really sure 32 is the correct size?

Its a size that works, while the current state does not work at all.

> I know 32 it what it had before, but the reason for the commit you
> quote was to improve performance ...

The commit above broke 32bit. Whoever wants to improve performance on
this dead horse can submit another patch.

Olaf