From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nikolaus Rath Subject: Re: lvmcache performance Date: Mon, 08 Feb 2016 14:05:24 -0800 Message-ID: <87mvrarh7f.fsf@thinkpad.rath.org> References: <87a8nctl7x.fsf@vostro.rath.org> <20160208091705.GA1612@rh-vpn> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from out2-smtp.messagingengine.com ([66.111.4.26]:55117 "EHLO out2-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756756AbcBHWF1 convert rfc822-to-8bit (ORCPT ); Mon, 8 Feb 2016 17:05:27 -0500 Received: from compute3.internal (compute3.nyi.internal [10.202.2.43]) by mailout.nyi.internal (Postfix) with ESMTP id A27C0207E2 for ; Mon, 8 Feb 2016 17:05:26 -0500 (EST) Received: from ebox.rath.org (ebox.rath.org [45.79.69.51]) by mail.messagingengine.com (Postfix) with ESMTPA id 55AA9680154 for ; Mon, 8 Feb 2016 17:05:26 -0500 (EST) Received: from thinkpad.rath.org (thinkpad [192.168.12.2]) by ebox.rath.org (Postfix) with ESMTPS id 4FA361CC874 for ; Mon, 8 Feb 2016 22:05:25 +0000 (UTC) In-Reply-To: <20160208091705.GA1612@rh-vpn> (Joe Thornber's message of "Mon, 8 Feb 2016 09:17:06 +0000") Sender: linux-bcache-owner@vger.kernel.org List-Id: linux-bcache@vger.kernel.org To: linux-bcache@vger.kernel.org On Feb 08 2016, Joe Thornber wrote: > On Sun, Feb 07, 2016 at 10:43:30AM -0800, Nikolaus Rath wrote: >> Is that the wrong expectation? But even then, shouldn't I at least s= ee >> some improvement? > > Firstly, if you have the latest software, I suggest you switch to the > smq cache policy which is generally out performing the old mq policy > substantially. Will try, thanks. > Secondly, I think you may need to reset your expectations a bit. > dm-cache is a slow moving cache. It monitors IO, detectings hotspots > on the disk and then 'promotes' those regions to the SSD. You may > find that the reads that occur during a boot, occur only infrequently > once the system is booted. Well, yes, but since in my case the cache is bigger than the origin, shouldn't eventually *everything* end-up in the cache? Is there a way to tell how often I need to access a block for it to be promoted? I was hoping that the {read,write}_promote_adjustement settings would actually cause promotion on the first access. Best, -Nikolaus (No Cc on replies please, I'm reading the list) --=20 GPG encrypted emails preferred. Key id: 0xD113FCAC3C4E599F =46ingerprint: ED31 791B 2C5C 1613 AF38 8B8A D113 FCAC 3C4E 599F =C2=BBTime flies like an arrow, fruit flies like a Banana.= =C2=AB