From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752754AbcFIR0M (ORCPT ); Thu, 9 Jun 2016 13:26:12 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:19838 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752191AbcFIR0K (ORCPT ); Thu, 9 Jun 2016 13:26:10 -0400 X-IBM-Helo: d03dlp03.boulder.ibm.com X-IBM-MailFrom: jejb@linux.vnet.ibm.com X-IBM-RcptTo: olaf@aepfle.de;devel@linuxdriverproject.org;haiyangz@microsoft.com;kys@microsoft.com;martin.petersen@oracle.com;linux-kernel@vger.kernel.org;linux-scsi@vger.kernel.org Subject: Re: [PATCH v3] storvsc: use small sg_tablesize on x86 From: James Bottomley To: Olaf Hering , "K. Y. Srinivasan" , Haiyang Zhang , "Martin K. Petersen" Cc: devel@linuxdriverproject.org, linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org Date: Thu, 09 Jun 2016 10:25:59 -0700 In-Reply-To: <20160609162553.10290-1-olaf@aepfle.de> References: <20160609162553.10290-1-olaf@aepfle.de> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.16.5 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16060917-0008-0000-0000-000004C1AAE8 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16060917-0009-0000-0000-000038392936 Message-Id: <1465493159.2259.14.camel@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-06-09_05:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1604210000 definitions=main-1606090190 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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? That caps transfers at 128 k. Even in the dim, dark, pre-64bit (at least on x86) days, our static limit for sg tablesize was 128 (0.5M). I know 32 it what it had before, but the reason for the commit you quote was to improve performance ... James