Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753460AbZGTMOz (ORCPT ); Mon, 20 Jul 2009 08:14:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751625AbZGTMOy (ORCPT ); Mon, 20 Jul 2009 08:14:54 -0400 Received: from e39.co.us.ibm.com ([32.97.110.160]:37751 "EHLO e39.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751482AbZGTMOy (ORCPT ); Mon, 20 Jul 2009 08:14:54 -0400 Date: Mon, 20 Jul 2009 17:44:50 +0530 From: Balbir Singh To: Izik Eidus Cc: akpm@linux-foundation.org, hugh.dickins@tiscali.co.uk, aarcange@redhat.com, chrisw@redhat.com, avi@redhat.com, riel@redhat.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, nickpiggin@yahoo.com.au Subject: Re: [PATCH 10/10] ksm: change ksm nice level to be 5 Message-ID: <20090720121450.GG24157@balbir.in.ibm.com> Reply-To: balbir@linux.vnet.ibm.com References: <1247851850-4298-4-git-send-email-ieidus@redhat.com> <1247851850-4298-5-git-send-email-ieidus@redhat.com> <1247851850-4298-6-git-send-email-ieidus@redhat.com> <1247851850-4298-7-git-send-email-ieidus@redhat.com> <1247851850-4298-8-git-send-email-ieidus@redhat.com> <1247851850-4298-9-git-send-email-ieidus@redhat.com> <1247851850-4298-10-git-send-email-ieidus@redhat.com> <1247851850-4298-11-git-send-email-ieidus@redhat.com> <20090720045037.GA24157@balbir.in.ibm.com> <4A645974.3020801@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <4A645974.3020801@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2076 Lines: 68 * Izik Eidus [2009-07-20 14:48:04]: > Balbir Singh wrote: >> * Izik Eidus [2009-07-17 20:30:50]: >> >> >>> From: Izik Eidus >>> >>> ksm should try not to disturb other tasks as much as possible. >>> >>> Signed-off-by: Izik Eidus >>> --- >>> mm/ksm.c | 2 +- >>> 1 files changed, 1 insertions(+), 1 deletions(-) >>> >>> diff --git a/mm/ksm.c b/mm/ksm.c >>> index 75d7802..4afe345 100644 >>> --- a/mm/ksm.c >>> +++ b/mm/ksm.c >>> @@ -1270,7 +1270,7 @@ static void ksm_do_scan(unsigned int scan_npages) >>> >>> static int ksm_scan_thread(void *nothing) >>> { >>> - set_user_nice(current, 0); >>> + set_user_nice(current, 5); >>> >> >> Is the 5 arbitrary? Why not +19? What is the intention of this change >> - to run when no other task is ready to run? >> > > Hey Balbir, > > I thought about giving it the lowest priority of nice before I did this > patch, but then I came into understanding that it isn't right, > Although ksm should not distrub other tasks while they are running, it > does need to run while they are running, > most of the use cases for ksm is to find identical pages in real time > while they are changing in the application, so giving it the lowest > priority doesn't seems right to me, > > But my understanding of how the nice prioritys are working is just my > intuition, so if you know better and think that for the use case i > described above other nice priority is better fit, tell me and I wont > have any problem to change. > > I was just checking to see why 5? May be it might be a good idea to document or at-least have rules on what priorities kernel threads can take? >> >>> while (!kthread_should_stop()) { >>> if (ksm_run & KSM_RUN_MERGE) { >>> >> >> > -- Balbir -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/