Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756606Ab1FDLZF (ORCPT ); Sat, 4 Jun 2011 07:25:05 -0400 Received: from casper.infradead.org ([85.118.1.10]:36391 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756100Ab1FDLZE convert rfc822-to-8bit (ORCPT ); Sat, 4 Jun 2011 07:25:04 -0400 Subject: Re: [patch] sched, cgroups: fix MIN_SHARES on 64 bit boxen From: Peter Zijlstra To: Mike Galbraith Cc: LKML , Nikhil Rao , Ingo Molnar In-Reply-To: <1307179796.25172.3.camel@marge.simson.net> References: <1307179796.25172.3.camel@marge.simson.net> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Sat, 04 Jun 2011 13:24:49 +0200 Message-ID: <1307186689.2353.4648.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1612 Lines: 41 On Sat, 2011-06-04 at 11:29 +0200, Mike Galbraith wrote: > c8b28116 claimed to have no user-visible effect, but allows setting cpu.shares > to < MIN_SHARES, which the user then indeed sees. > > Signed-off-by: Mike Galbraith > --- > kernel/sched.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > Index: linux-2.6/kernel/sched.c > =================================================================== > --- linux-2.6.orig/kernel/sched.c > +++ linux-2.6/kernel/sched.c > @@ -292,7 +292,7 @@ static DEFINE_SPINLOCK(task_group_lock); > * (The default weight is 1024 - so there's no practical > * limitation from this.) > */ > -#define MIN_SHARES 2 > +#define MIN_SHARES (scale_load(2)) > #define MAX_SHARES (1UL << (18 + SCHED_LOAD_RESOLUTION)) > > static int root_task_group_load = ROOT_TASK_GROUP_LOAD; Hurm, but that destroys most of the gains from that patch, the whole point was being able to have finer graunlarities, but now calc_cfs_shares() and effective_load() are clipped the coarse granularity. So maybe explicitly change the MIN_SHARES usage in sched_group_set_shares(). That wants to become a clamp user anyway, something like: shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES)); That way MAX_SHARES can also loose its SCHED_LOAD_RESOLUTION factor and bring is back in line with MIN_SHARES. -- 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/