From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joe Thornber Subject: Re: [PATCH] [dm-cache] Make the mq policy an alias for smq Date: Thu, 11 Feb 2016 10:10:02 +0000 Message-ID: <20160211101001.GA4908@rh-vpn> References: <1455100523-16922-1-git-send-email-ejt@redhat.com> <22203.28152.788363.168128@quad.stoffel.home> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <22203.28152.788363.168128@quad.stoffel.home> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: John Stoffel Cc: Joe Thornber , dm-devel@redhat.com List-Id: dm-devel.ids On Wed, Feb 10, 2016 at 12:06:00PM -0500, John Stoffel wrote: > > Can you add in some documentation on how you tell which dm_cache > policy is actually being used, and how to measure it, etc? It's a > black box and some info would be nice. You can get some stats on the cache performance via the status ioctl (eg, dmsetup status ...). This will tell you about promotions/demotion to the cache, write hits, read hits etc. There is documentation on cache policies in Documentation/device-mapper/cache-policies.txt https://github.com/jthornber/linux-2.6/blob/2016-02-10-thin-dev-on-4.4/Documentation/device-mapper/cache-policies.txt As for knowing which policy is running; I'm not sure what to say. It'll be the one you ask for. If the above patch goes in, then there'll be a kernel version where mq becomes the same as smq. I'll bump the policy version number to make it clear that mq has undergone a big change. - Joe