From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7B3D2C433DB for ; Mon, 21 Dec 2020 22:50:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1C83222573 for ; Mon, 21 Dec 2020 22:50:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726131AbgLUWum (ORCPT ); Mon, 21 Dec 2020 17:50:42 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36688 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725782AbgLUWul (ORCPT ); Mon, 21 Dec 2020 17:50:41 -0500 Received: from mail-ej1-x62d.google.com (mail-ej1-x62d.google.com [IPv6:2a00:1450:4864:20::62d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 403BAC0613D6 for ; Mon, 21 Dec 2020 14:50:01 -0800 (PST) Received: by mail-ej1-x62d.google.com with SMTP id qw4so15654410ejb.12 for ; Mon, 21 Dec 2020 14:50:01 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=/hmLBcYgvXk/x1QAZ2dN9muAY4mPZk3wo3lefglzomQ=; b=m2lkABdNRFWgCF0kTj5BZWNL0Rc4i1eL8zJPrX3hcPsLfz0Quc+SSfK47kI3dxN0/c BpzvlzzzXcTdCpRXHaqu5jcPDWj3zp8O3Ikkh71CwRwslu4zBdQGnTsueG87GKyWmiPd kKnu03OEbS5rIk0ODvwacGLyJAis8/lzDDEsQr221koX6aJrJc2Upxyu+yDuvKlqMwDg 2guRE156sk5EfAp5ADH15uDPeBRp/PzNnVl6g+H0vn6V1WKBBE7a3FdYgwAe6ywKWTzy pL700BDm4GW6KhuvwLWvW7NFQQpMv4nX9fIYwTsE5R961AzPlAO/oUotqX7r1bo7StsS vCQw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=/hmLBcYgvXk/x1QAZ2dN9muAY4mPZk3wo3lefglzomQ=; b=RbjITy4zYv6YMOPQdUo5hywEnhawm0cexq1B5uvn53o7szcH7k0YeD3tNdKtt+yO3K iaCTmlR6dkvvgDT6uL2HB3p6ZKou4dGMetNQbUiOCoFjRqqs2iskL6ihfSMgNNL91Zyc PNeC7djB+wIpww4VxpYGQDphy5rErNuQ5fyciQStPc84/Z+EpxW0AsuI/TIU94QqXZtp EvaZyk4cKyy2nj6VQV+IKguH6mUDgRRG1Iw2dZ54EjRha6D/u/yHWCKz5Tl/FS3bXd31 8StIrY20p2QTrnI+4A07mtPlEATjHZ4YW7GmsOHoFRCdkbacBihL+c/uIdIQb8e6H9Hr Ujsg== X-Gm-Message-State: AOAM532QhGgOeoWvA8+COESaBCBfKdOAsdWP/Vp1lEb/HRMcAKZccBJk ydbRWBeR9odRstgipgMxhvZ6OqEsvJNQGsyCRNg= X-Google-Smtp-Source: ABdhPJxmefuwPRoZDrpPvJC9+uE3rnDPwK10MaE5CZD5KnWRCq91cueqEbd9TQLMPFrGF1cG96/MLP3gG1+EzkDY/Gw= X-Received: by 2002:a17:906:52d9:: with SMTP id w25mr17050247ejn.504.1608591000044; Mon, 21 Dec 2020 14:50:00 -0800 (PST) MIME-Version: 1.0 References: <20201218201633.2735367-1-jonathan.lemon@gmail.com> <20201218201633.2735367-4-jonathan.lemon@gmail.com> <20201221191835.ic3aln6ib5hbftlk@bsd-mbp> In-Reply-To: <20201221191835.ic3aln6ib5hbftlk@bsd-mbp> From: Willem de Bruijn Date: Mon, 21 Dec 2020 17:49:22 -0500 Message-ID: Subject: Re: [PATCH 3/9 v1 RFC] skbuff: replace sock_zerocopy_put() with skb_zcopy_put() To: Jonathan Lemon Cc: Network Development , Eric Dumazet , Kernel Team Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org > > > All uargs should have a callback function, (unless nouarg > > > is set), so push all special case logic handling down into > > > the callbacks. This slightly pessimizes the refcounted cases, > > > > What does this mean? > > The current zerocopy_put() code does: > 1) if uarg, dec refcount, if refcount == 0: > if callback, run callback, else consume skb. > > This is called from the main TCP/UDP send path. These would be called > for the zctap case as well, so it should be made generic - not specific > to the current zerocopy implementation. The patch changes this into: > > 1) if uarg, run callback. > > Then, the msg_zerocopy code does: > > 1) save state, > 2) dec refcount, run rest of callback on 0. > > Which is the same as before. The !uarg case is never handled here. > The zctap cases switch to their own callbacks. > > > The current zerocopy clear code does: > 1) if no_uarg, skip > 2) if msg_zerocopy, save state, dec refcount, run callback when 0. > 3) otherwise just run callback. > 4) clear flags > > I would like to remove the msg_zerocopy specific logic from the function, > so this becomes: > > 1) if uarg, run callback. > 2) clear flags That sounds fine. Especially since we can simplify the logic after the commit I mentioned. I just didn't understand what you meant by pessimize. > > > -void sock_zerocopy_callback(struct ubuf_info *uarg, bool success) > > > +static void __sock_zerocopy_callback(struct ubuf_info *uarg) > > > { > > > struct sk_buff *tail, *skb = skb_from_uarg(uarg); > > > struct sock_exterr_skb *serr; > > > @@ -1222,7 +1222,7 @@ void sock_zerocopy_callback(struct ubuf_info *uarg, bool success) > > > serr->ee.ee_origin = SO_EE_ORIGIN_ZEROCOPY; > > > serr->ee.ee_data = hi; > > > serr->ee.ee_info = lo; > > > - if (!success) > > > + if (!uarg->zerocopy) > > > serr->ee.ee_code |= SO_EE_CODE_ZEROCOPY_COPIED; > > > > > > q = &sk->sk_error_queue; > > > @@ -1241,18 +1241,15 @@ void sock_zerocopy_callback(struct ubuf_info *uarg, bool success) > > > consume_skb(skb); > > > sock_put(sk); > > > } > > > -EXPORT_SYMBOL_GPL(sock_zerocopy_callback); > > > > > > -void sock_zerocopy_put(struct ubuf_info *uarg) > > > +void sock_zerocopy_callback(struct ubuf_info *uarg, bool success) > > > { > > > - if (uarg && refcount_dec_and_test(&uarg->refcnt)) { > > > - if (uarg->callback) > > > - uarg->callback(uarg, uarg->zerocopy); > > > - else > > > - consume_skb(skb_from_uarg(uarg)); > > > > I suppose this can be removed after commit 0a4a060bb204 ("sock: fix > > zerocopy_success regression with msg_zerocopy"). Cleaning that up > > would better be a separate patch that explains why the removal is > > safe. > > I'll split the patches out. Thanks. Yes, splitting that patch in two will help (me) follow it better. > > > It's also fine to bundle with moving refcount_dec_and_test into > > sock_zerocopy_callback, which indeed follows from it. > > > > > - } > > > + uarg->zerocopy = uarg->zerocopy & success; > > > + > > > + if (refcount_dec_and_test(&uarg->refcnt)) > > > + __sock_zerocopy_callback(uarg); > > > > This can be wrapped in existing sock_zerocopy_callback. No need for a > > __sock_zerocopy_callback. > > The compiler will inline the helper anyway, since it's a single > callsite. True. I just don't think the wrapper adds much value here.