Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754381Ab0F1TMB (ORCPT ); Mon, 28 Jun 2010 15:12:01 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:38721 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753299Ab0F1TL7 (ORCPT ); Mon, 28 Jun 2010 15:11:59 -0400 Date: Mon, 28 Jun 2010 12:10:56 -0700 From: Andrew Morton To: Minchan Kim Cc: Johannes Weiner , KOSAKI Motohiro , Larry Woodman , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [Patch] Call cond_resched() at bottom of main look in balance_pgdat() Message-Id: <20100628121056.408cbca2.akpm@linux-foundation.org> In-Reply-To: References: <20100622112416.B554.A69D9226@jp.fujitsu.com> <20100622114739.B563.A69D9226@jp.fujitsu.com> <20100622213301.GA26285@cmpxchg.org> X-Mailer: Sylpheed 2.4.8 (GTK+ 2.12.9; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1297 Lines: 31 On Wed, 23 Jun 2010 08:07:34 +0900 Minchan Kim wrote: > Acked-by: Johannes Weiner > Reviewed-by: Minchan Kim > Reviewed-by: Rik van Riel > Reviewed-by: KOSAKI Motohiro The patch is a bit sucky, isn't it? a) the cond_resched() which Larry's patch adds is very special. It _looks_ like a random preemption point but it's actually critical to the correct functioning of the system. That's utterly unobvious to anyone who reads the code, so a comment explaining this *must* be included. b) cond_resched() is a really crappy way of solving the problem which Larry described. It will sit there chewing away CPU time until kswapd's timeslice expires. I suppose we can live with b) although it _does_ suck and I'd suggest that the comment include a big FIXME, so someone might fix it. Larry, please fix a), gather the acks and reviewed-by's, update the changelog to identify the commit which broke it and resend? -- 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/