From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with SMTP id 925AF6B008A for ; Wed, 8 Dec 2010 21:05:18 -0500 (EST) Date: Wed, 8 Dec 2010 18:05:14 -0800 From: Simon Kirby Subject: Re: [patch] mm: skip rebalance of hopeless zones Message-ID: <20101209020514.GE3796@hostway.ca> References: <1291821419-11213-1-git-send-email-hannes@cmpxchg.org> <20101209003621.GB3796@hostway.ca> <20101208172324.d45911f4.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20101208172324.d45911f4.akpm@linux-foundation.org> Sender: owner-linux-mm@kvack.org To: Andrew Morton Cc: Johannes Weiner , Mel Gorman , Rik van Riel , linux-mm@kvack.org List-ID: On Wed, Dec 08, 2010 at 05:23:24PM -0800, Andrew Morton wrote: > People at google have told me they've seen the same thing. A fork is > taking 15 minutes when someone else is doing a dd, because the fork > enters direct-reclaim trying for an order-one page. It successfully > frees some order-one pages but before it gets back to allocate one, dd > has gone and stolen them, or split them apart. > > This problem would have got worse when slub came along doing its stupid > unnecessary high-order allocations. Yeah, we can all blame slub, but even when I force everything to be order-0 except task_struct and kmalloc(>4096), I still see problems, even if they aren't as obvious. Until reclaim holds a page it is about to turn into an order-1, or until it can hold all of the pages until the watermark is reached including the allocation it may be directly reclaiming for, this operation is always going to be non-fair so long as kswapd can run while other allocations are happening. Let me guess, Linus will say RCU fixes this.. ;) Simon- -- 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/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org