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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1EBB0C7EE23 for ; Mon, 12 Jun 2023 13:05:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236273AbjFLNFj (ORCPT ); Mon, 12 Jun 2023 09:05:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46742 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236081AbjFLNF1 (ORCPT ); Mon, 12 Jun 2023 09:05:27 -0400 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 94F2810D8; Mon, 12 Jun 2023 06:05:24 -0700 (PDT) Received: from dggpemm500005.china.huawei.com (unknown [172.30.72.55]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4QfsHJ1yNwz18MB1; Mon, 12 Jun 2023 21:00:28 +0800 (CST) Received: from localhost.localdomain (10.69.192.56) by dggpemm500005.china.huawei.com (7.185.36.74) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.23; Mon, 12 Jun 2023 21:05:22 +0800 From: Yunsheng Lin To: , , CC: , , Yunsheng Lin , Lorenzo Bianconi , Alexander Duyck , Jesper Dangaard Brouer , Ilias Apalodimas , Eric Dumazet , Jonathan Corbet , Alexei Starovoitov , Daniel Borkmann , John Fastabend , , Subject: [PATCH net-next v4 5/5] page_pool: update document about frag API Date: Mon, 12 Jun 2023 21:02:56 +0800 Message-ID: <20230612130256.4572-6-linyunsheng@huawei.com> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20230612130256.4572-1-linyunsheng@huawei.com> References: <20230612130256.4572-1-linyunsheng@huawei.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Content-Type: text/plain; charset=US-ASCII X-Originating-IP: [10.69.192.56] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To dggpemm500005.china.huawei.com (7.185.36.74) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org As more drivers begin to use the frag API, update the document about how to decide which API to for the driver author. Also it seems there is a similar document in page_pool.h, so remove it to avoid the duplication. Signed-off-by: Yunsheng Lin CC: Lorenzo Bianconi CC: Alexander Duyck --- Documentation/networking/page_pool.rst | 34 +++++++++++++++++++++----- include/net/page_pool.h | 22 ----------------- 2 files changed, 28 insertions(+), 28 deletions(-) diff --git a/Documentation/networking/page_pool.rst b/Documentation/networking/page_pool.rst index 873efd97f822..df3e28728008 100644 --- a/Documentation/networking/page_pool.rst +++ b/Documentation/networking/page_pool.rst @@ -4,12 +4,28 @@ Page Pool API ============= -The page_pool allocator is optimized for the XDP mode that uses one frame -per-page, but it can fallback on the regular page allocator APIs. - -Basic use involves replacing alloc_pages() calls with the -page_pool_alloc_pages() call. Drivers should use page_pool_dev_alloc_pages() -replacing dev_alloc_pages(). +The page_pool allocator is optimized for recycling page or page frag used by skb +packet and xdp frame. + +Basic use involves replacing alloc_pages() calls with different page pool +allocator API based on different use case: +1. page_pool_alloc_pages(): allocate memory without page splitting when driver + knows that the memory it need is always bigger than half of the page + allocated from page pool. There is no cache line dirtying for 'struct page' + when a page is recycled back to the page pool. + +2. page_pool_alloc_frag(): allocate memory with page splitting when driver knows + that the memory it need is always smaller than or equal to half of the page + allocated from page pool. Page splitting enables memory saving and thus avoid + TLB/cache miss for data access, but there also is some cost to implement page + splitting, mainly some cache line dirtying/bouncing for 'struct page' and + atomic operation for page->pp_frag_count. + +3. page_pool_alloc(): allocate memory with or without page splitting depending + on the requested memory size when driver doesn't know the size of memory it + need beforehand. It is a mix of the above two case, so it is a wrapper of the + above API to simplify driver's interface for memory allocation with least + memory utilization and performance penalty. API keeps track of in-flight pages, in order to let API user know when it is safe to free a page_pool object. Thus, API users @@ -93,6 +109,12 @@ a page will cause no race conditions is enough. * page_pool_dev_alloc_pages(): Get a page from the page allocator or page_pool caches. +* page_pool_dev_alloc_frag(): Get a page frag from the page allocator or + page_pool caches. + +* page_pool_dev_alloc(): Get a page or page frag from the page allocator or + page_pool caches. + * page_pool_get_dma_addr(): Retrieve the stored DMA address. * page_pool_get_dma_dir(): Retrieve the stored DMA direction. diff --git a/include/net/page_pool.h b/include/net/page_pool.h index f4fc339ff020..5fea37fd7767 100644 --- a/include/net/page_pool.h +++ b/include/net/page_pool.h @@ -5,28 +5,6 @@ * Copyright (C) 2016 Red Hat, Inc. */ -/** - * DOC: page_pool allocator - * - * This page_pool allocator is optimized for the XDP mode that - * uses one-frame-per-page, but have fallbacks that act like the - * regular page allocator APIs. - * - * Basic use involve replacing alloc_pages() calls with the - * page_pool_alloc_pages() call. Drivers should likely use - * page_pool_dev_alloc_pages() replacing dev_alloc_pages(). - * - * API keeps track of in-flight pages, in-order to let API user know - * when it is safe to dealloactor page_pool object. Thus, API users - * must make sure to call page_pool_release_page() when a page is - * "leaving" the page_pool. Or call page_pool_put_page() where - * appropiate. For maintaining correct accounting. - * - * API user must only call page_pool_put_page() once on a page, as it - * will either recycle the page, or in case of elevated refcnt, it - * will release the DMA mapping and in-flight state accounting. We - * hope to lift this requirement in the future. - */ #ifndef _NET_PAGE_POOL_H #define _NET_PAGE_POOL_H -- 2.33.0