From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f199.google.com (mail-pf0-f199.google.com [209.85.192.199]) by kanga.kvack.org (Postfix) with ESMTP id A44726B0005 for ; Wed, 20 Jul 2016 16:59:02 -0400 (EDT) Received: by mail-pf0-f199.google.com with SMTP id p64so122731464pfb.0 for ; Wed, 20 Jul 2016 13:59:02 -0700 (PDT) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id y67si5266056pfy.250.2016.07.20.13.59.01 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 20 Jul 2016 13:59:01 -0700 (PDT) Date: Wed, 20 Jul 2016 13:59:00 -0700 From: Andrew Morton Subject: Re: [PATCH 04/17] arm: get rid of superfluous __GFP_REPEAT Message-Id: <20160720135900.6735fc0db41807c2edf88594@linux-foundation.org> In-Reply-To: <20160601162424.GD19428@n2100.arm.linux.org.uk> References: <1464599699-30131-1-git-send-email-mhocko@kernel.org> <1464599699-30131-5-git-send-email-mhocko@kernel.org> <20160601162424.GD19428@n2100.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Russell King - ARM Linux Cc: Michal Hocko , linux-mm@kvack.org, LKML , Michal Hocko , linux-arch@vger.kernel.org On Wed, 1 Jun 2016 17:24:24 +0100 Russell King - ARM Linux wrote: > On Mon, May 30, 2016 at 11:14:46AM +0200, Michal Hocko wrote: > > From: Michal Hocko > > > > __GFP_REPEAT has a rather weak semantic but since it has been introduced > > around 2.6.12 it has been ignored for low order allocations. > > > > PGALLOC_GFP uses __GFP_REPEAT but none of the allocation which uses > > this flag is for more than order-2. This means that this flag has never > > been actually useful here because it has always been used only for > > PAGE_ALLOC_COSTLY requests. > > I hear what you say, but... > > commit 8c65da6dc89ccb605d73773b1dd617e72982d971 > Author: Russell King > Date: Sat Nov 30 12:52:31 2013 +0000 > > ARM: pgd allocation: retry on failure > > Make pgd allocation retry on failure; we really need this to succeed > otherwise fork() can trigger OOMs. > > Signed-off-by: Russell King > > and that's the change which introduced this, and it did solve a problem > for me. So I'm not happy to give an ack for this change unless someone > can tell me why adding __GFP_REPEAT back then had a beneficial effect. > Maybe there was some other bug in the MM layer in 2013 which this change > happened to solve? I suspect that some other change has made arm's use of __GFP_REPEAT unnecessary, because __GFP_REPEAT is now a no-op for order-0,1,2,3 allocations and none of the arm callsites which I can see are using order-4 or higher. So I think we should go ahead with this change. If that causes some problem then we'll need to dig in and figure out why the impossible just happened, OK? -- 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