From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail190.messagelabs.com (mail190.messagelabs.com [216.82.249.51]) by kanga.kvack.org (Postfix) with ESMTP id 647216B0047 for ; Tue, 28 Sep 2010 18:00:46 -0400 (EDT) Date: Tue, 28 Sep 2010 22:57:30 +0100 From: Russell King - ARM Linux Subject: Re: [patch] arch: remove __GFP_REPEAT for order-0 allocations Message-ID: <20100928215730.GC8649@n2100.arm.linux.org.uk> References: <20100928143655.4282a001.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100928143655.4282a001.akpm@linux-foundation.org> Sender: owner-linux-mm@kvack.org To: Andrew Morton Cc: David Rientjes , Arnd Bergmann , Richard Henderson , Ivan Kokshaysky , Matt Turner , Mikael Starvik , Jesper Nilsson , David Howells , Geert Uytterhoeven , Roman Zippel , Michal Simek , Koichi Yasutake , Kyle McMartin , Helge Deller , Benjamin Herrenschmidt , Paul Mackerras , Martin Schwidefsky , Heiko Carstens , Paul Mundt , "David S. Miller" , Jeff Dike , Ingo Molnar , "H. Peter Anvin" , Thomas Gleixner , linux-arch@vger.kernel.org, linux-mm@kvack.org List-ID: On Tue, Sep 28, 2010 at 02:36:55PM -0700, Andrew Morton wrote: > On Tue, 28 Sep 2010 03:45:10 -0700 (PDT) > David Rientjes wrote: > > > Order-0 allocations, including quicklist_alloc(), are always under > > PAGE_ALLOC_COSTLY_ORDER, so they loop endlessly in the page allocator > > already without the need for __GFP_REPEAT. > > That's only true for the current implementation of the page allocator. > > If we were to change the page allocator behaviour to not do that (and > we change it daily!) then all those callsites which wanted __GFP_REPEAT > behaviour will get broken. So someone would need to go back and work > out how to unbreak them, if we remembered. > > Plus there's presumably some documentary benefit in leaving the > __GFP_REPEATs in there. > > Why are those __GFP_REPEATs present at those callsites? What were > developers trying to achieve? As I understand it, it's come about by way of evolution. I think (I can't check) that we had loops in the allocation functions. These were removed and replaced by __GFP_REPEATs sometime before the current GIT history started. I'd check on bkbits.net which I'm sure will have it, but unfortunately I can't get access to the history for include/asm-arm/pgalloc.h prior to its move to arch/arm. -- 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