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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS 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 07D4BC43441 for ; Sat, 17 Nov 2018 20:01:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B6C282080C for ; Sat, 17 Nov 2018 20:01:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B6C282080C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=davemloft.net Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726741AbeKRGSv (ORCPT ); Sun, 18 Nov 2018 01:18:51 -0500 Received: from shards.monkeyblade.net ([23.128.96.9]:34322 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725732AbeKRGSv (ORCPT ); Sun, 18 Nov 2018 01:18:51 -0500 Received: from localhost (unknown [IPv6:2601:601:9f80:35cd::bf5]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) (Authenticated sender: davem-davemloft) by shards.monkeyblade.net (Postfix) with ESMTPSA id E5C901420C0C6; Sat, 17 Nov 2018 12:01:05 -0800 (PST) Date: Sat, 17 Nov 2018 12:01:05 -0800 (PST) Message-Id: <20181117.120105.1022512033566284108.davem@davemloft.net> To: jasowang@redhat.com Cc: mst@redhat.com, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next 1/2] vhost_net: mitigate page reference counting during page frag refill From: David Miller In-Reply-To: <20181115094310.17307-1-jasowang@redhat.com> References: <20181115094310.17307-1-jasowang@redhat.com> X-Mailer: Mew version 6.8 on Emacs 26.1 Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Sat, 17 Nov 2018 12:01:06 -0800 (PST) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Jason Wang Date: Thu, 15 Nov 2018 17:43:09 +0800 > We do a get_page() which involves a atomic operation. This patch tries > to mitigate a per packet atomic operation by maintaining a reference > bias which is initially USHRT_MAX. Each time a page is got, instead of > calling get_page() we decrease the bias and when we find it's time to > use a new page we will decrease the bias at one time through > __page_cache_drain_cache(). > > Testpmd(virtio_user + vhost_net) + XDP_DROP on TAP shows about 1.6% > improvement. > > Before: 4.63Mpps > After: 4.71Mpps > > Signed-off-by: Jason Wang Applied.