From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?ISO-8859-1?Q?Luis_Pab=F3n?= Subject: Re: Cache tier READ_FORWARD transition Date: Mon, 07 Jul 2014 17:03:37 -0400 Message-ID: <53BB0B29.6080807@redhat.com> References: <53BACB03.5010603@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mx1.redhat.com ([209.132.183.28]:36870 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751205AbaGGVDk (ORCPT ); Mon, 7 Jul 2014 17:03:40 -0400 Received: from int-mx09.intmail.prod.int.phx2.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id s67L3d1X001266 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK) for ; Mon, 7 Jul 2014 17:03:39 -0400 In-Reply-To: Sender: ceph-devel-owner@vger.kernel.org List-ID: To: Sage Weil Cc: "ceph-devel@vger.kernel.org" I think so, but I am not sure what kind of workload would benefit from that tune. Do you have any in mind? Is the reason for this tuneable value to have a more storage efficient caching tier? - Luis On 07/07/2014 03:29 PM, Sage Weil wrote: > On Mon, 7 Jul 2014, Luis Pabon wrote: >> Hi all, >> I am working on OSDMonitor.cc:5325 and wanted to confirm the following >> read_forward cache tier transition: >> >> readforward -> forward || writeback || (any && num_objects_dirty == 0) >> forward -> writeback || readforward || (any && num_objects_dirty == 0) >> writeback -> readforward || forward >> >> Is this the correct cache tier state transition? > That looks right to me. > > By the way, I had a thought after we spoke that we probably want something > that is somewhere inbetween the current writeback behavior (promote on > first read) and the read_forward behavior (never promote on read). I > suspect a good all-around policy is something like promote on second read? > This should probably be rolled into the writeback mode as a tunable... > > sage > >