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 AC2BA6B003D for ; Fri, 1 May 2009 08:06:29 -0400 (EDT) Date: Fri, 1 May 2009 13:05:50 +0100 (BST) From: Hugh Dickins Subject: Re: [PATCH mmotm] mm: alloc_large_system_hash check order In-Reply-To: <49FAE12F.4020005@cosmosbay.com> Message-ID: References: <20090430132544.GB21997@csn.ul.ie> <49FAE12F.4020005@cosmosbay.com> MIME-Version: 1.0 Content-Type: MULTIPART/MIXED; BOUNDARY="8323584-246501030-1241179429=:11574" Sender: owner-linux-mm@kvack.org To: Eric Dumazet Cc: Mel Gorman , Andrew Morton , Andi Kleen , David Miller , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --8323584-246501030-1241179429=:11574 Content-Type: TEXT/PLAIN; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE On Fri, 1 May 2009, Eric Dumazet wrote: > Hugh Dickins a =C3=A9crit : > > On Thu, 30 Apr 2009, Mel Gorman wrote: > >> On Wed, Apr 29, 2009 at 10:09:48PM +0100, Hugh Dickins wrote: > >>> On an x86_64 with 4GB ram, tcp_init()'s call to alloc_large_system_ha= sh(), > >>> to allocate tcp_hashinfo.ehash, is now triggering an mmotm WARN_ON_ON= CE on > >>> order >=3D MAX_ORDER - it's hoping for order 11. alloc_large_system_= hash() > >>> had better make its own check on the order. >=20 > Well, I dont know why, since alloc_large_system_hash() already take > care of retries, halving size between each tries. Sorry, I wasn't clear: I just meant that if we keep that WARN_ON_ONCE(order >=3D MAX_ORDER) in __alloc_pages_slowpath(), then we need alloc_large_system_hash() to avoid the call to __get_free_pages() in the order >=3D MAX_ORDER case, precisely because we're happy with the way it halves and falls back, so don't want a noisy warning; and now that we know that it could give that warning, it would be a shame for the _ONCE to suppress more interesting warnings later. I certainly did not mean for alloc_large_system_hash() to fail in the order >=3D MAX_ORDER case, nor did the patch do so. Hugh --8323584-246501030-1241179429=:11574-- -- 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