From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 1 Jun 2006 20:04:05 +0200 From: Jens Axboe Subject: Re: NCQ performance (was Re: [rfc][patch] remove racy sync_page?) Message-ID: <20060601180405.GP4400@suse.de> References: <20060601131921.GH4400@suse.de> <447F0023.8090206@argo.co.il> <20060601150320.GO4400@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060601150320.GO4400@suse.de> Sender: owner-linux-mm@kvack.org Return-Path: To: Avi Kivity Cc: Mark Lord , Linus Torvalds , Nick Piggin , linux-kernel@vger.kernel.org, linux-mm@kvack.org, mason@suse.com, andrea@suse.de, hugh@veritas.com List-ID: On Thu, Jun 01 2006, Jens Axboe wrote: > On Thu, Jun 01 2006, Avi Kivity wrote: > > Jens Axboe wrote: > > > > > >Ok, I decided to rerun a simple random read work load (with fio), using > > >depths 1 and 32. The test is simple - it does random reads all over the > > >drive size with 4kb block sizes. The reads are O_DIRECT. The test > > >pattern was set to repeatable, so it's going through the same workload. > > >The test spans the first 32G of the drive and runtime is capped at 20 > > >seconds. > > > > > > > Did you modify the iodepth given to the test program, or to the drive? > > If the former, then some of the performance increase came from the Linux > > elevator. > > > > Ideally exactly the same test would be run with the just the drive > > parameters changed. > > Just from the program. Since the software depth matched the software > depth, I'd be surprised if it made much of a difference here. I can > rerun the same test tomorrow with the drive depth modified the and > software depth fixed at 32. Then the io scheduler can at least help the > drive without NCQ out somewhat. Same test, but with iodepth=48 for both ncq depth 1 and ncq depth 31. This gives the io scheduler something to work with for both cases. sda: Maxtor 7B300S0 sdb: Maxtor 7L320S0 sdc: SAMSUNG HD160JJ sdd: HDS725050KLA360 (Hitachi 500GB drive) drive depth KiB/sec diff diff 1/1 ---------------------------------------------------------------- sda 1/1 397 sda 1 513 +29% sda 31 673 +31+ +69% sdb 1/1 397 sdb 1 535 +35% sdb 31 741 +38% +87% sdc 1/1 372 sdc 1 449 +21% sdc 31 507 +13% +36% sdd 1/1 489 sdd 1 650 +33% sdd 31 941 +45% +92% Conclusions: the io scheduler helps, NCQ help - both combined helps a lot. The Samsung firmware looks bad. Additional requests in io scheduler when using NCQ doesn't help, except for the new firmware Maxtor. Suspect. NCQ still helps a lot, > 30% for all drives except the Samsung. -- Jens Axboe -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org