From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Snitzer Subject: Re: [PATCH 7/7] dm: optimize clone_rq() when track_peak_rq_based_ios is disabled Date: Thu, 12 Sep 2013 19:06:46 -0400 Message-ID: <20130912230646.GA31577@redhat.com> References: <1379024698-10487-1-git-send-email-snitzer@redhat.com> <1379024698-10487-8-git-send-email-snitzer@redhat.com> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: Mikulas Patocka Cc: dm-devel@redhat.com, Frank Mayhar List-Id: dm-devel.ids On Thu, Sep 12 2013 at 7:00pm -0400, Mikulas Patocka wrote: > > > On Thu, 12 Sep 2013, Mike Snitzer wrote: > > > Make use of static keys to eliminate the relevant branch in clone_rq() > > when dm_mod's 'track_peak_rq_based_ios' paramter is set to 0 (disabled). > > > > Even if 'track_peak_rq_based_ios' is set to 0 it will not take effect > > until the next request-based table reload. Once it is disabled the > > 'peak_rq_based_ios' parameter will be reset to 0. > > This patch changes it so that the value track_peak_rq_based_ios is sampled > only when reloading a table. I think it will be confusing to the user if > he changes the value, but the change doesn't take effect until something > reloads some table. Well we need to be able to notice the change but I do not wish to do so in a performance critical path (which clone_rq is).