From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030215AbWFIPlq (ORCPT ); Fri, 9 Jun 2006 11:41:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030221AbWFIPlq (ORCPT ); Fri, 9 Jun 2006 11:41:46 -0400 Received: from e33.co.us.ibm.com ([32.97.110.151]:49293 "EHLO e33.co.us.ibm.com") by vger.kernel.org with ESMTP id S1030219AbWFIPlp (ORCPT ); Fri, 9 Jun 2006 11:41:45 -0400 Message-ID: <44899562.6010609@in.ibm.com> Date: Fri, 09 Jun 2006 21:06:02 +0530 From: Balbir Singh Reply-To: balbir@in.ibm.com Organization: IBM India Private Limited User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.12) Gecko/20051205 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Andrew Morton Cc: nagar@watson.ibm.com, jlan@sgi.com, csturtiv@sgi.com, linux-kernel@vger.kernel.org Subject: Re: [Patch][RFC] Disabling per-tgid stats on task exit in taskstats References: <44892610.6040001@watson.ibm.com> <20060609010057.e454a14f.akpm@osdl.org> <448952C2.1060708@in.ibm.com> <20060609042129.ae97018c.akpm@osdl.org> In-Reply-To: <20060609042129.ae97018c.akpm@osdl.org> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Andrew Morton wrote: > On Fri, 09 Jun 2006 16:21:46 +0530 > Balbir Singh wrote: > > >>Andrew Morton wrote: >> >>>On Fri, 09 Jun 2006 03:41:04 -0400 >>>Shailabh Nagar wrote: >>> >>> >>> >>>>Hence, this patch introduces a configuration parameter >>>> /sys/kernel/taskstats_tgid_exit >>>>through which a privileged user can turn on/off sending of per-tgid stats on >>>>task exit. >>> >>> >>>That seems a bit clumsy. What happens if one consumer wants the per-tgid >>>stats and another does not? >> >>For all subsystems that re-use the taskstats structure from the exit path, >>we have the issue that you mentioned. Thats because several statistics co-exist >>in the same structure. These subsystems can keep their tgid-stats empty by not >>filling up anything in fill_tgid() or using this patch to selectively enable/disable >>tgid stats. >> >>For other subsystems, they could pass tgidstats as NULL to taskstats_exit_send(). >> > > > I don't understand. If a subsystem exists then it fills in its slots in > the taskstats structure, doesn't it? > > No other subsystem needs a global knob, does it? > > You see the problem - if one userspace package wants the tgid-stats and > another concurrently-running one does now, what do we do? Just leave it > enabled and run a bit slower? Another option is to get the package to define their own taskstats genetlink attribute and fill it up in taskstats_exit_send(). This would be similar to TASKSTATS_TYPE_AGGR_PID/TGID. They can make this attribute independent of the taskstats structure and fill it based on their policy (per-pid or per-tgid). But the current interface users like CSA want to build on top of the taskstats structure. > > If so, how much slower? Your changelog says some potential users don't > need the tgid-stats, but so what? I assume this patch is a performance > thing? If so, has it been quantified? > -- Balbir Singh, Linux Technology Center, IBM Software Labs