From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [PATCH 04/10] net: pad skb data and shinfo as a whole rather than individually Date: Tue, 10 Apr 2012 17:01:30 +0200 Message-ID: <1334070090.5300.59.camel@edumazet-glaptop> References: <1334067965.5394.22.camel@zakaz.uk.xensource.com> <1334067984-7706-4-git-send-email-ian.campbell@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, David Miller , "Michael S. Tsirkin" , Wei Liu , xen-devel@lists.xen.org To: Ian Campbell Return-path: Received: from mail-bk0-f46.google.com ([209.85.214.46]:41746 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758897Ab2DJPBk (ORCPT ); Tue, 10 Apr 2012 11:01:40 -0400 Received: by bkcik5 with SMTP id ik5so4305694bkc.19 for ; Tue, 10 Apr 2012 08:01:39 -0700 (PDT) In-Reply-To: <1334067984-7706-4-git-send-email-ian.campbell@citrix.com> Sender: netdev-owner@vger.kernel.org List-ID: On Tue, 2012-04-10 at 15:26 +0100, Ian Campbell wrote: > This reduces the minimum overhead required for this allocation such that the > shinfo can be grown in the following patch without overflowing 2048 bytes for a > 1500 byte frame. > > Reducing this overhead while also growing the shinfo means that sometimes the > tail end of the data can end up in the same cache line as the beginning of the > shinfo. Specifically in the case of the 64 byte cache lines on a 64 bit system > the first 8 bytes of shinfo can overlap the tail cacheline of the data. In many > cases the allocation slop means that there is no overlap. > > Signed-off-by: Ian Campbell > Cc: "David S. Miller" > Cc: Eric Dumazet > --- Acked-by: Eric Dumazet