From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with ESMTP id 5DB406B01B0 for ; Mon, 28 Jun 2010 15:11:51 -0400 (EDT) Date: Mon, 28 Jun 2010 12:10:56 -0700 From: Andrew Morton 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> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Minchan Kim Cc: Johannes Weiner , KOSAKI Motohiro , Larry Woodman , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org