From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Bottomley Subject: Re: [Bug 10846] Slow write on LSISAS1068E (SAS6/iR) on kernel >= 2.6.22 Date: Tue, 03 Jun 2008 15:15:22 -0500 Message-ID: <1212524122.3329.16.camel@localhost.localdomain> References: <20080603160902.B120A10805D@picon.linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: Received: from accolon.hansenpartnership.com ([76.243.235.52]:33365 "EHLO accolon.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754096AbYFCUP1 (ORCPT ); Tue, 3 Jun 2008 16:15:27 -0400 In-Reply-To: <20080603160902.B120A10805D@picon.linux-foundation.org> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: bugme-daemon@bugzilla.kernel.org Cc: linux-scsi@vger.kernel.org On Tue, 2008-06-03 at 09:09 -0700, bugme-daemon@bugzilla.kernel.org wrote: > Should we consider, that such a difference is normal. You suggest that before > the kernel was dangerous at writing data? It's caching too much streaming data, yes. The danger is largely the amount of data you lose on a crash and mismanagement of the cache starving other applications. It's not that much of a problem. At an estimated write speed of ~70MB/s your 1GB of data is only around 15s to effect a full writeout. > So unpacking linux kernel (for example) is 5x times slower and it is not a > problem. That's just new way of caching data? We seldom see crashes (thanks to > linux) and we have power supply. There are many factors that could account for that. > I'd like testing on same hardware windows to see its behaviour and speed. > Anyway thanks for the clarifying of cache: write through. As you say, it was > not evident. > > So, now, what can we do to keep 2.6.21 behaviour? That's for a mail system > writing lots of little files and performance matters too. Well, initially, I'd try a benchmark that simulates the actual problem, like postmark. A streaming write tells you very little about the entire system performance under a mail server type load. James