From patchwork Fri Jul 14 17:08:51 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexander Lobakin X-Patchwork-Id: 13313869 X-Patchwork-Delegate: kuba@kernel.org Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 70085156C1 for ; Fri, 14 Jul 2023 17:10:54 +0000 (UTC) Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 197763ABC; Fri, 14 Jul 2023 10:10:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1689354646; x=1720890646; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=lhIzZFfcEcJps7lcQP/nAxoYlG5hsQcTY92/w+e8fV0=; b=i5V95Dfo6doULw0JXaLxr92vplBvnp7Tjj7oNrBmEImxmIACcM7mbQex kF7wyvl2e4vX5zrOG82GFIzQYQm655fsn3RJK5oQAN1D0jZfC0AEDGdAm It61f+Y9JcaykvHySfdTandDnPgyWXZExUCTa7yNg1y4ZndPAiRzujuwT oDFgLq6d9W2puC5ylPSNjXDlz26wcTJxFJwkq4QV20SXcRtR+NFe5c0nY hoHjryQsApt3q5y61heYQO4Brc0Uct+zXTkvpaeJIVo8FKc9ju6lHe4iY jaSKdsJrqZ/HkmZVeJ8pld4tzeq1ykmaudeYqlCskWs3i58FkcgrK8dKw Q==; X-IronPort-AV: E=McAfee;i="6600,9927,10771"; a="451891946" X-IronPort-AV: E=Sophos;i="6.01,206,1684825200"; d="scan'208";a="451891946" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Jul 2023 10:10:45 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10771"; a="787907090" X-IronPort-AV: E=Sophos;i="6.01,206,1684825200"; d="scan'208";a="787907090" Received: from newjersey.igk.intel.com ([10.102.20.203]) by fmsmga008.fm.intel.com with ESMTP; 14 Jul 2023 10:10:41 -0700 From: Alexander Lobakin To: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Cc: Alexander Lobakin , Maciej Fijalkowski , Larysa Zaremba , Yunsheng Lin , Alexander Duyck , Jesper Dangaard Brouer , Ilias Apalodimas , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH RFC net-next v2 6/7] net: skbuff: avoid accessing page_pool if !napi_safe when returning page Date: Fri, 14 Jul 2023 19:08:51 +0200 Message-ID: <20230714170853.866018-9-aleksander.lobakin@intel.com> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230714170853.866018-1-aleksander.lobakin@intel.com> References: <20230714170853.866018-1-aleksander.lobakin@intel.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED, SPF_HELO_NONE,SPF_NONE,T_SCC_BODY_TEXT_LINE,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net X-Patchwork-Delegate: kuba@kernel.org X-Patchwork-State: RFC Currently, pp->p.napi is always read, but the actual variable it gets assigned to is read-only when @napi_safe is true. For the !napi_safe cases, which yet is still a pack, it's an unneeded operation. Moreover, it can lead to premature or even redundant page_pool cacheline access. For example, when page_pool_is_last_frag() returns false (with the recent frag improvements). Thus, read it only when @napi_safe is true. This also allows moving @napi inside the condition block itself. Constify it while we are here, because why not. Signed-off-by: Alexander Lobakin --- net/core/skbuff.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 4de280c454e4..fc1470aab5cf 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -881,9 +881,8 @@ static void skb_clone_fraglist(struct sk_buff *skb) bool page_pool_return_skb_page(struct page *page, bool napi_safe) { - struct napi_struct *napi; + bool allow_direct = false; struct page_pool *pp; - bool allow_direct; page = compound_head(page); @@ -903,9 +902,12 @@ bool page_pool_return_skb_page(struct page *page, bool napi_safe) * in the same context as the consumer would run, so there's * no possible race. */ - napi = READ_ONCE(pp->p.napi); - allow_direct = napi_safe && napi && - READ_ONCE(napi->list_owner) == smp_processor_id(); + if (napi_safe) { + const struct napi_struct *napi = READ_ONCE(pp->p.napi); + + allow_direct = napi && + READ_ONCE(napi->list_owner) == smp_processor_id(); + } /* Driver set this to memory recycling info. Reset it on recycle. * This will *not* work for NIC using a split-page memory model.