Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754287AbdGSXNU (ORCPT ); Wed, 19 Jul 2017 19:13:20 -0400 Received: from mx2.suse.de ([195.135.220.15]:42677 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754181AbdGSXLq (ORCPT ); Wed, 19 Jul 2017 19:11:46 -0400 Date: Wed, 19 Jul 2017 16:11:34 -0700 From: Davidlohr Bueso To: Andrew Morton Cc: "Eric W. Biederman" , Elena Reshetova , linux-kernel@vger.kernel.org, peterz@infradead.org, gregkh@linuxfoundation.org, mingo@redhat.com, adobriyan@gmail.com, serge@hallyn.com, arozansk@redhat.com, keescook@chromium.org, Hans Liljestrand , David Windsor Subject: Re: [PATCH 1/3] ipc: convert ipc_namespace.count from atomic_t to refcount_t Message-ID: <20170719231134.GF14395@linux-80c1.suse> References: <1499417992-3238-1-git-send-email-elena.reshetova@intel.com> <1499417992-3238-2-git-send-email-elena.reshetova@intel.com> <87bmottgo4.fsf@xmission.com> <20170719153546.37567fbf77861653172fa263@linux-foundation.org> <20170719225427.GD14395@linux-80c1.suse> <20170719155833.641a283467bf6b89a7d2e56b@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20170719155833.641a283467bf6b89a7d2e56b@linux-foundation.org> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1208 Lines: 36 On Wed, 19 Jul 2017, Andrew Morton wrote: >On Wed, 19 Jul 2017 15:54:27 -0700 Davidlohr Bueso wrote: > >> On Wed, 19 Jul 2017, Andrew Morton wrote: >> >> >I do rather dislike these conversions from the point of view of >> >performance overhead and general code bloat. But I seem to have lost >> >that struggle and I don't think any of these are fastpath(?). >> >> Well, since we now have fd25d19 (locking/refcount: Create unchecked atomic_t >> implementation), performance is supposed to be ok. > >Sure, things are OK for people who disable the feature. > >But for people who want to enable the feature we really should minimize >the cost by avoiding blindly converting sites which simply don't need >it: simple, safe, old, well-tested code. Why go and slow down such >code? Need to apply some common sense here... Fair points. > >> It would be lovely to have >> some actual numbers nonetheless. > >Very much so. May I suggest using mmtests with the following config file: https://github.com/gormanm/mmtests/blob/7e070a810bc0af92e592e5121d0ea75fada51aeb/configs/config-global-dhp__workload-ipc-scale-short It will run two of Manfred's ipcscale sem benchmarks. Thanks, Davidlohr