From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [PATCH] tcp: avoid order-1 allocations on wifi and tx path Date: Wed, 11 Apr 2012 09:38:02 +0200 Message-ID: <1334129882.5300.2539.camel@edumazet-glaptop> References: <20120409.143710.879746943062854492.davem@davemloft.net> <4F83316F.20504@lwfinger.net> <1333998672.3007.245.camel@edumazet-glaptop> <20120409.153452.1284163346306246866.davem@davemloft.net> <1334030180.13293.98.camel@edumazet-glaptop> <20120410051127.GA32048@merlins.org> <1334038263.2907.1.camel@edumazet-glaptop> <20120411052733.GA17352@merlins.org> <1334122980.5300.2154.camel@edumazet-glaptop> <1334125848.5300.2330.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Larry.Finger-tQ5ms3gMjBLk1uMJSBkQmQ@public.gmane.org, bhutchings-s/n/eUQHGBpZroRs9YW3xA@public.gmane.org, linux-wireless-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Marc MERLIN , David Miller Return-path: In-Reply-To: <1334125848.5300.2330.camel@edumazet-glaptop> Sender: linux-wireless-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: netdev.vger.kernel.org On Wed, 2012-04-11 at 08:30 +0200, Eric Dumazet wrote: > Marc Merlin reported many order-1 allocations failures in TX path on its > wireless setup, that dont make any sense with MTU=1500 network, and non > SG capable hardware. > > After investigation, it turns out TCP uses sk_stream_alloc_skb() and > used as a convention skb_tailroom(skb) to know how many bytes of data > payload could be put in this skb (for non SG capable devices) > ... > > Reported-by: Marc MERLIN > Tested-by: Marc MERLIN > Signed-off-by: Eric Dumazet David, I forgot to say this should be backported to 3.2 & 3.3 commit 87fb4b7b533073 (net: more accurate skb truesize) did the placement of skb_shared_info at the end of skb head, so sk_stream_alloc_skb() had to reserve more room so that tailroom stayed at MSS -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html