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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 DE0A4C433B4 for ; Fri, 14 May 2021 08:31:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 989A3613C3 for ; Fri, 14 May 2021 08:31:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231510AbhENIdF (ORCPT ); Fri, 14 May 2021 04:33:05 -0400 Received: from szxga06-in.huawei.com ([45.249.212.32]:2982 "EHLO szxga06-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229704AbhENIdE (ORCPT ); Fri, 14 May 2021 04:33:04 -0400 Received: from dggems703-chm.china.huawei.com (unknown [172.30.72.60]) by szxga06-in.huawei.com (SkyGuard) with ESMTP id 4FhMC70TmVzld9h; Fri, 14 May 2021 16:29:39 +0800 (CST) Received: from dggpemm500005.china.huawei.com (7.185.36.74) by dggems703-chm.china.huawei.com (10.3.19.180) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Fri, 14 May 2021 16:31:51 +0800 Received: from [127.0.0.1] (10.69.30.204) by dggpemm500005.china.huawei.com (7.185.36.74) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.2176.2; Fri, 14 May 2021 16:31:51 +0800 Subject: Re: [PATCH net-next v5 3/5] page_pool: Allow drivers to hint on SKB recycling To: Ilias Apalodimas CC: Matteo Croce , , , Ayush Sawal , "Vinay Kumar Yadav" , Rohit Maheshwari , "David S. Miller" , Jakub Kicinski , Thomas Petazzoni , Marcin Wojtas , Russell King , Mirko Lindner , Stephen Hemminger , "Tariq Toukan" , Jesper Dangaard Brouer , "Alexei Starovoitov" , Daniel Borkmann , "John Fastabend" , Boris Pismenny , Arnd Bergmann , Andrew Morton , "Peter Zijlstra (Intel)" , Vlastimil Babka , Yu Zhao , Will Deacon , Fenghua Yu , Roman Gushchin , Hugh Dickins , Peter Xu , Jason Gunthorpe , Jonathan Lemon , Alexander Lobakin , Cong Wang , wenxu , Kevin Hao , Jakub Sitnicki , Marco Elver , Willem de Bruijn , Miaohe Lin , Guillaume Nault , , , , Matthew Wilcox , Eric Dumazet , David Ahern , Lorenzo Bianconi , Saeed Mahameed , Andrew Lunn , Paolo Abeni , Sven Auhagen References: <20210513165846.23722-1-mcroce@linux.microsoft.com> <20210513165846.23722-4-mcroce@linux.microsoft.com> <798d6dad-7950-91b2-46a5-3535f44df4e2@huawei.com> From: Yunsheng Lin Message-ID: <212498cf-376b-2dac-e1cd-12c7cc7910c6@huawei.com> Date: Fri, 14 May 2021 16:31:50 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 8bit X-Originating-IP: [10.69.30.204] X-ClientProxiedBy: dggeme705-chm.china.huawei.com (10.1.199.101) To dggpemm500005.china.huawei.com (7.185.36.74) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On 2021/5/14 15:36, Ilias Apalodimas wrote: > [...] >>> + return false; >>> + >>> + pp = (struct page_pool *)page->pp; >>> + >>> + /* Driver set this to memory recycling info. Reset it on recycle. >>> + * This will *not* work for NIC using a split-page memory model. >>> + * The page will be returned to the pool here regardless of the >>> + * 'flipped' fragment being in use or not. >>> + */ >>> + page->pp = NULL; >> >> Why not only clear the page->pp when the page can not be recycled >> by the page pool? so that we do not need to set and clear it every >> time the page is recycled。 >> > > If the page cannot be recycled, page->pp will not probably be set to begin > with. Since we don't embed the feature in page_pool and we require the > driver to explicitly enable it, as part of the 'skb flow', I'd rather keep > it as is. When we set/clear the page->pp, the page is probably already in > cache, so I doubt this will have any measurable impact. The point is that we already have the skb->pp_recycle to let driver to explicitly enable recycling, as part of the 'skb flow, if the page pool keep the page->pp while it owns the page, then the driver may only need to call one skb_mark_for_recycle() for a skb, instead of call skb_mark_for_recycle() for each page frag of a skb. Maybe we can add a parameter in "struct page_pool_params" to let driver to decide if the page pool ptr is stored in page->pp while the page pool owns the page? Another thing accured to me is that if the driver use page from the page pool to form a skb, and it does not call skb_mark_for_recycle(), then there will be resource leaking, right? if yes, it seems the skb_mark_for_recycle() call does not seems to add any value? > >>> + page_pool_put_full_page(pp, virt_to_head_page(data), false); >>> + >>> C(end); > > [...]