From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758000Ab3E0WZY (ORCPT ); Mon, 27 May 2013 18:25:24 -0400 Received: from mail-pa0-f49.google.com ([209.85.220.49]:40534 "EHLO mail-pa0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751245Ab3E0WZX (ORCPT ); Mon, 27 May 2013 18:25:23 -0400 Message-ID: <1369693520.3301.477.camel@edumazet-glaptop> Subject: Re: [Patch v2] skbuff: Hide GFP_ATOMIC page allocation failures for dropped packets From: Eric Dumazet To: Rik van Riel Cc: atomlin@redhat.com, netdev@vger.kernel.org, davem@davemloft.net, edumazet@google.com, pshelar@nicira.com, mst@redhat.com, alexander.h.duyck@intel.com, aquini@redhat.com, sergei.shtylyov@cogentembedded.com, linux-kernel@vger.kernel.org Date: Mon, 27 May 2013 15:25:20 -0700 In-Reply-To: <51A39A3F.8080903@redhat.com> References: <1369599557-22677-1-git-send-email-atomlin@redhat.com> <51A39A3F.8080903@redhat.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3-0ubuntu6 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2013-05-27 at 13:39 -0400, Rik van Riel wrote: > On 05/26/2013 04:19 PM, atomlin@redhat.com wrote: > > From: Aaron Tomlin > > > > Since v1: > > - Removed unnecessary parentheses > > > > ---8<--- > > > > Failed GFP_ATOMIC allocations by the network stack result in dropped > > packets, which will be received on a subsequent retransmit, and an > > unnecessary, noisy warning with a kernel backtrace. This claim is wrong, only some protocols deal with retransmits. > > > > These warnings are harmless, but they still cause users to panic and > > file bug reports over dropped packets. It would be better to hide the > > failed allocation warnings and backtraces, and let retransmits handle > > dropped packets quietly. > > Yes please. Getting memory management bug reports for > dropped network packets got old years ago. Lets get > rid of those messages. I am only wondering why this path has anything needing special attention, over thousands of kmalloc() like call sites in the kernel. If mm allocation warnings are useless, just make __GFP_NOWARN the default, and save us thousand of patches (adding the __GFP_NOWARN everywhere) Truth is : some network drivers don't deal very well with allocation errors. mlx4 for example absolutely wants order-2 pages in RX path, with no fallback to order-0 pages. So I am not against this patch, but I can not really acknowledge it, sorry.