From patchwork Wed Jan 13 05:12:07 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Dumazet X-Patchwork-Id: 362658 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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=ham 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 367C4C433DB for ; Wed, 13 Jan 2021 05:13:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DB03F23117 for ; Wed, 13 Jan 2021 05:12:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725849AbhAMFMy (ORCPT ); Wed, 13 Jan 2021 00:12:54 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58582 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725773AbhAMFMx (ORCPT ); Wed, 13 Jan 2021 00:12:53 -0500 Received: from mail-pl1-x62d.google.com (mail-pl1-x62d.google.com [IPv6:2607:f8b0:4864:20::62d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 77F0CC061575 for ; Tue, 12 Jan 2021 21:12:13 -0800 (PST) Received: by mail-pl1-x62d.google.com with SMTP id q4so409062plr.7 for ; Tue, 12 Jan 2021 21:12:13 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=KS9zKNWnlZGMGSJTeN3Ir6H+5nEXyxOsPC5vJwRtu+g=; b=XC/fvuhzI/yJ5M8v/CgD4GuZQ9OkgL/hseuvUCr96nAG4UYrx58j2FrCq4676mnl4M Uxyq6gM/3oV+Oz7v4fQEcDTq7U/PA3mBr+/7fJQs3RMwHCAb/Gq0N5iu8vUH2dLevgj4 fGYKB1oDuNyHl4dwYob94iH9LQ7fF8fJAHaJ1aHBA6r9JRXQjweLVBEzGYLPDeQHhVA2 SivdTsMR2iQX5UdzZXHVYm5ZmbFnPUc4j2EMOUl8x+quv6C/R+W9nTU+f6TFqeIJsvjO 5/M4dykWV2ziP3ELc+c+di0dr3DMv3VA6eo6+NQtppiDVY7G9t9lM0lEr/oKnpVpgorP HmDg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=KS9zKNWnlZGMGSJTeN3Ir6H+5nEXyxOsPC5vJwRtu+g=; b=Sm0Xdo89qnBd02grchChKJFo73u7ZkCYHpoVRI7UouEVw7Psc3ifwqedT+JAGLW/W9 7KmF2cCQAfplILGuDZM2m4DKoyEvHvBT5l/g3aJS6P5Rg6eWkuTL93Qy1R1xaAxChW+t ol7lrucMbvupM6LmvbPwchXANQ2Z7rjwTDA3ul98kHQ+T4lrX1giM/KjE+COzDlqQSDB rMa76kJCAi1/29Ez5/fOE/GFyLVm+5SsKlN0oEhpEnNPqewd2lRQ6S/f/NbivkzAXOQo 42nBwk8/KW1C34xgyMNJRXKocD1HwmOFIx/utaZddL/0CTdeOdxXd/9gmCuw73XkVegO J0YQ== X-Gm-Message-State: AOAM5336v6/57ykdGy+SHQVogxakYxglr6zWKt64n+hoETiZtiVP6kZk Iew9FlXjm5h1f1vZRurkkhA= X-Google-Smtp-Source: ABdhPJzYceds6v61I5AsDBBdpZv2YENBzM3Qoy23smYpIGZG2nFOIO0aI4bpekMwrxFPqc/5wQLIJQ== X-Received: by 2002:a17:902:ea94:b029:da:a547:b6a6 with SMTP id x20-20020a170902ea94b02900daa547b6a6mr569504plb.78.1610514733121; Tue, 12 Jan 2021 21:12:13 -0800 (PST) Received: from edumazet1.svl.corp.google.com ([2620:15c:2c4:201:7220:84ff:fe09:1424]) by smtp.gmail.com with ESMTPSA id h24sm913974pfq.13.2021.01.12.21.12.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 12 Jan 2021 21:12:12 -0800 (PST) From: Eric Dumazet To: "David S . Miller" , Jakub Kicinski Cc: netdev , Eric Dumazet , Eric Dumazet , Paolo Abeni , "Michael S . Tsirkin" , Greg Thelen Subject: [PATCH net] Revert "virtio_net: replace netdev_alloc_skb_ip_align() with napi_alloc_skb()" Date: Tue, 12 Jan 2021 21:12:07 -0800 Message-Id: <20210113051207.142711-1-eric.dumazet@gmail.com> X-Mailer: git-send-email 2.30.0.284.gd98b1dd5eaa7-goog MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Eric Dumazet This reverts commit c67f5db82027ba6d2ea4ac9176bc45996a03ae6a. While using page fragments instead of a kmalloc backed skb->head might give a small performance improvement in some cases, there is a huge risk of memory use under estimation. GOOD_COPY_LEN is 128 bytes. This means that we need a small amount of memory to hold the headers and struct skb_shared_info Yet, napi_alloc_skb() might use a whole 32KB page (or 64KB on PowerPc) for long lived incoming TCP packets. We have been tracking OOM issues on GKE hosts hitting tcp_mem limits but consuming far more memory for TCP buffers than instructed in tcp_mem[2] Even if we force napi_alloc_skb() to only use order-0 pages, the issue would still be there on arches with PAGE_SIZE >= 32768 Using alloc_skb() and thus standard kmallloc() for skb->head allocations will get the benefit of letting other objects in each page being independently used by other skbs, regardless of the lifetime. Note that a similar problem exists for skbs allocated from napi_get_frags(), this is handled in a separate patch. I would like to thank Greg Thelen for his precious help on this matter, analysing crash dumps is always a time consuming task. Signed-off-by: Eric Dumazet Cc: Paolo Abeni Cc: Michael S. Tsirkin Cc: Greg Thelen --- drivers/net/virtio_net.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 508408fbe78fbd8658dc226834b5b1b334b8b011..5886504c1acacf3f6148127b5c1cc7f6a906b827 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -386,7 +386,7 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi, p = page_address(page) + offset; /* copy small packet so we can reuse these pages for small data */ - skb = napi_alloc_skb(&rq->napi, GOOD_COPY_LEN); + skb = netdev_alloc_skb_ip_align(vi->dev, GOOD_COPY_LEN); if (unlikely(!skb)) return NULL;