From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [PATCH net-next] net: netdev_alloc_skb() use build_skb() Date: Mon, 04 Jun 2012 21:29:45 +0200 Message-ID: <1338838185.2760.1899.camel@edumazet-glaptop> References: <1337272404.3403.18.camel@edumazet-glaptop> <20120517164016.GL14498@1wt.eu> <1337273387.3403.24.camel@edumazet-glaptop> <1337276056.3403.37.camel@edumazet-glaptop> <20120604123738.GA28992@redhat.com> <1338815213.2760.1806.camel@edumazet-glaptop> <20120604134138.GA29814@redhat.com> <1338818501.2760.1821.camel@edumazet-glaptop> <20120604141731.GA30226@redhat.com> <1338822064.2760.1834.camel@edumazet-glaptop> <20120604181623.GF32205@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Willy Tarreau , David Miller , netdev@vger.kernel.org To: "Michael S. Tsirkin" Return-path: Received: from mail-bk0-f46.google.com ([209.85.214.46]:51884 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750912Ab2FDT3u (ORCPT ); Mon, 4 Jun 2012 15:29:50 -0400 Received: by bkcji2 with SMTP id ji2so3932619bkc.19 for ; Mon, 04 Jun 2012 12:29:49 -0700 (PDT) In-Reply-To: <20120604181623.GF32205@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: On Mon, 2012-06-04 at 21:16 +0300, Michael S. Tsirkin wrote: > Yes but if a tcp socket then hangs on, on one of the fragments, > while the other has been freed, the whole page is still > never reused, right? > > Doesn't this mean truesize should be 4K? > Yes, or more exactly PAGE_SIZE, but then performance would really go down on machines with 64KB pages. Maybe we should make the whole frag head idea enabled only for PAGE_SIZE=4096. Not sure we want to track precise truesize, as the minimum truesize is SKB_DATA_ALIGN(length + NET_SKB_PAD) + SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) (64 + 64 + 320) = 448 Its not like buggy drivers that used truesize = length