Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932510Ab3FQJyX (ORCPT ); Mon, 17 Jun 2013 05:54:23 -0400 Received: from mail-ob0-f181.google.com ([209.85.214.181]:48072 "EHLO mail-ob0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755983Ab3FQJyW (ORCPT ); Mon, 17 Jun 2013 05:54:22 -0400 MIME-Version: 1.0 In-Reply-To: <51B2948A.60309@intel.com> References: <1370590169-24804-1-git-send-email-alex.shi@intel.com> <1370590169-24804-2-git-send-email-alex.shi@intel.com> <51B2948A.60309@intel.com> Date: Mon, 17 Jun 2013 11:54:21 +0200 Message-ID: Subject: Re: [RFC patch 1/4] sched: change cfs_rq load avg to unsigned long From: Vincent Guittot To: Alex Shi Cc: "mingo@redhat.com" , Peter Zijlstra , Thomas Gleixner , Andrew Morton , Borislav Petkov , Paul Turner , Namhyung Kim , Mike Galbraith , Morten Rasmussen , Preeti U Murthy , Viresh Kumar , linux-kernel , Mel Gorman , riel@redhat.com, Michael Wang , Jason Low Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1939 Lines: 51 On 8 June 2013 04:18, Alex Shi wrote: > On 06/07/2013 05:07 PM, Vincent Guittot wrote: >> On 7 June 2013 09:29, Alex Shi wrote: >>> > Since the 'u64 runnable_load_avg, blocked_load_avg' in cfs_rq struct are >>> > smaller than 'unsigned long' cfs_rq->load.weight. We don't need u64 >>> > vaiables to describe them. unsigned long is more efficient and convenience. >>> > >> Hi Alex, >> >> I just want to point out that we can't have more than 48388 tasks with >> highest priority on a runqueue with an unsigned long on a 32 bits >> system. I don't know if we can reach such kind of limit on a 32bits >> machine ? For sure, not on an embedded system. > > Thanks question! > It should be a talked problem. I just remember the conclusion is when > you get the up bound task number, you already run out the memory space > on 32 bit. > > Just for kernel resource for a process, it need 2 pages stack. > mm_struct, task_struct, task_stats, vm_area_struct, page table etc. > these are already beyond 4 pages. so 4 * 4k * 48388 = 774MB. plus user > level resources. > > So, usually the limited task number in Linux is often far lower this > number: $ulimit -u. > > Anyway, at least, the runnable_load_avg is smaller then load.weight. if > load.weight can use long type, runablle_load_avg is no reason can't. Alex, You can add my tested-by for this patchset. Regards, Vincent > > -- > Thanks > Alex > -- > 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/ -- 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/