From mboxrd@z Thu Jan 1 00:00:00 1970 From: Don Brace Subject: RE: [PATCH] sd: preserve sysfs updates to max_sectors_kb Date: Tue, 29 Aug 2017 22:32:04 +0000 Message-ID: <4993A297653ECB4581FA5C3C31323D195B8E9288@avsrvexchmbx1.microsemi.net> References: <150309002518.8999.15900049133748830764.stgit@brunhilda> <1503090353.2622.15.camel@wdc.com> <4993A297653ECB4581FA5C3C31323D195B8D825D@avsrvexchmbx2.microsemi.net> <1503092817.2622.19.camel@wdc.com> <4993A297653ECB4581FA5C3C31323D195B8DBDE4@avsrvexchmbx2.microsemi.net> <1503345191.2571.13.camel@wdc.com> ,<4993A297653ECB4581FA5C3C31323D195B8DBE34@avsrvexchmbx2.microsemi.net> <4993A297653ECB4581FA5C3C31323D195B8E9103@avsrvexchmbx1.microsemi.net> ,<1504030401.2653.43.camel@wdc.com> ,<4993A297653ECB4581FA5C3C31323D195B8E9143@avsrvexchmbx1.microsemi.net> <4993A297653ECB4581FA5C3C31323D195B8E9191@avsrvexchmbx1.microsemi.net>,<1504045532.2653.68.camel@wdc.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Return-path: Received: from mail-co1nam03on0088.outbound.protection.outlook.com ([104.47.40.88]:8301 "EHLO NAM03-CO1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751290AbdH2WcJ (ORCPT ); Tue, 29 Aug 2017 18:32:09 -0400 In-Reply-To: <1504045532.2653.68.camel@wdc.com> Content-Language: en-US Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Bart Van Assche , "hch@infradead.org" , Viswas G , Gerry Morong , Mahesh Rajashekhara , "POSWALD@suse.com" , Scott Benesh , Bader Ali - Saleh , Kevin Barnett , "joseph.szczypek@hpe.com" , Scott Teel , "jejb@linux.vnet.ibm.com" , Justin Lindley , John Hall Cc: "linux-scsi@vger.kernel.org" ________________________________________=0A= From: Bart Van Assche [Bart.VanAssche@wdc.com]=0A= Sent: Tuesday, August 29, 2017 3:25 PM=0A= To: hch@infradead.org; Viswas G; Gerry Morong; Mahesh Rajashekhara; POSWALD= @suse.com; Scott Benesh; Don Brace; Bader Ali - Saleh; Kevin Barnett; josep= h.szczypek@hpe.com; Scott Teel; jejb@linux.vnet.ibm.com; Justin Lindley; Jo= hn Hall=0A= Cc: linux-scsi@vger.kernel.org=0A= Subject: Re: [PATCH] sd: preserve sysfs updates to max_sectors_kb=0A= =0A= EXTERNAL EMAIL=0A= =0A= =0A= On Tue, 2017-08-29 at 19:41 +0000, Don Brace wrote:=0A= > BLKRRPART ends up in the sd driver function sd_revalidate_disk, which res= ets=0A= > q->limits.max_sectors =3D min(rw_max, queue_max_hw_sectors(q));= =0A= > back to the value from VPD page 0xb0.=0A= >=0A= > When you cat out max_sectors_kb, it obtains it's valuse from q->limits.ma= x_sectors=0A= >=0A= > Adding a udev rule... Will there be a delay between the watch rule and th= e new rule?=0A= =0A= Hello Don,=0A= =0A= In your original e-mail you wrote that max_sectors_kb was tuned because=0A= of performance reasons. So does it really matter that for a very short=0A= time max_sectors_kb does not have the optimal value?=0A= =0A= > One more point, what will I change the value back to? The watch rule=0A= > changed it and I do not have the original value.=0A= =0A= To the value you want to set max_sectors_kb to.=0A= =0A= Bart.=0A= =0A= Users do set max_sectors_kb for performance reasons. They can increase=0A= performance by setting max_sectors_kb to different values depending on=0A= their I/O needs.=0A= =0A= And, if they set the value, and sd_revalidate_disk changes this value, =0A= there is no history of what they set the value to. =0A= =0A= Thanks,=0A= Don Brace=0A= Microsemi Corp.=0A= =0A=