From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: Slow perfs with IDE SSD Date: Thu, 13 Jul 2006 01:32:57 +0900 Message-ID: <44B52439.80408@gmail.com> References: <44B52182.3020008@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from nz-out-0102.google.com ([64.233.162.200]:48008 "EHLO nz-out-0102.google.com") by vger.kernel.org with ESMTP id S1750809AbWGLQbx (ORCPT ); Wed, 12 Jul 2006 12:31:53 -0400 Received: by nz-out-0102.google.com with SMTP id l1so167556nzf for ; Wed, 12 Jul 2006 09:31:53 -0700 (PDT) In-Reply-To: <44B52182.3020008@gmail.com> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: =?UTF-8?B?RnJhbsOnb2lzLUp1bGllbiBNYXJiYXVk?= Cc: linux-ide@vger.kernel.org Tejun Heo wrote: > Fran=C3=A7ois-Julien Marbaud wrote: >> Hi ! >> >> I'm doing an internship in a research lab, and we are trying to use = a=20 >> P.ATA SSD >> in order to speed-up a genome computation software. >> >> We got a performance problem, expecially with access time : access=20 >> time is about >> 800us, and according to the manufacturer it should be about 40us. Th= e=20 >> bandwith >> is OK. >> >> The SSD is a 2.5' flash hard drive, the slave of the first IDE chann= el. >> >> We wonder if that could be the because P.ATA driver is not really do= ne=20 >> for small >> access times, so we got such a poor time. In that case, I guess we=20 >> would have to >> have a closer look at the driver ...=20 >=20 > First of all, try noop elevator. >=20 > echo noop > /sys/block/hdx/queue/scheduler >=20 > Depending on your workload, adjusting plugging delay/threshold=20 > parameters might help. These are initialized in the kernel source fi= le=20 > block/ll_rw_blk.c::blk_queue_make_request(). q->unplug_thresh and=20 > q->unplug_delay. >=20 And one more thing, if a 67MB~4GB SDD drive speeds up the computation,=20 something is wrong. 4GB main memory will be much better than 4GB SDD=20 for such purposes. --=20 tejun