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 5808EC43470 for ; Fri, 14 May 2021 08:31:58 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A22D2613F5 for ; Fri, 14 May 2021 08:31:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A22D2613F5 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 201746B0036; Fri, 14 May 2021 04:31:57 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 1D88A6B006E; Fri, 14 May 2021 04:31:57 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 079696B0070; Fri, 14 May 2021 04:31:57 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0128.hostedemail.com [216.40.44.128]) by kanga.kvack.org (Postfix) with ESMTP id CA9576B0036 for ; Fri, 14 May 2021 04:31:56 -0400 (EDT) Received: from smtpin01.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 6DB94180300D9 for ; Fri, 14 May 2021 08:31:56 +0000 (UTC) X-FDA: 78139168632.01.ED4F4BC Received: from szxga06-in.huawei.com (szxga06-in.huawei.com [45.249.212.32]) by imf24.hostedemail.com (Postfix) with ESMTP id 5F04FA00039D for ; Fri, 14 May 2021 08:31:54 +0000 (UTC) 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 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 Authentication-Results: imf24.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=huawei.com; spf=pass (imf24.hostedemail.com: domain of linyunsheng@huawei.com designates 45.249.212.32 as permitted sender) smtp.mailfrom=linyunsheng@huawei.com X-Stat-Signature: 6jwcnte7yuprmy1aupiz6udnijjnyt43 X-Rspamd-Queue-Id: 5F04FA00039D X-Rspamd-Server: rspam02 X-HE-Tag: 1620981114-726942 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2021/5/14 15:36, Ilias Apalodimas wrote: > [...] >>> + return false; >>> + >>> + pp =3D (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 =3D 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=E3=80=82 >> >=20 > If the page cannot be recycled, page->pp will not probably be set to be= gin > 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 k= eep=20 > it as is. When we set/clear the page->pp, the page is probably already= in=20 > 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 k= eep the page->pp while it owns the page, then the driver may only need to cal= l one skb_mark_for_recycle() for a skb, instead of call skb_mark_for_recycl= e() 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? >=20 >>> + page_pool_put_full_page(pp, virt_to_head_page(data), false); >>> + >>> C(end); >=20 > [...]