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=-0.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 A3333C28CBC for ; Wed, 6 May 2020 11:57:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7DB6D20714 for ; Wed, 6 May 2020 11:57:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="fVO5Ddl3" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727964AbgEFL5s (ORCPT ); Wed, 6 May 2020 07:57:48 -0400 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:60178 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726924AbgEFL5s (ORCPT ); Wed, 6 May 2020 07:57:48 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1588766267; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=8SQDFnlIJbT5ua1JOyFwQCxTImV9nf4dY7BK+J1cBSE=; b=fVO5Ddl3bulPKi/gByVHCqOr/l1SwSAzqUlEHpfGrhQt23K29RCOY34MJi8OhOVNwhBIBd c4JjscmggfhcN8/OuTQ3fz4JSRJ9PUGXOVXLCdYHvkJA3CZWcm63fc01+BQnyfOKPbzfZr e9XnRRqA8t1+zri58pyTGAKlXlGOEm4= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-505-U8D4NsYRMluEvww3yfdbCw-1; Wed, 06 May 2020 07:57:45 -0400 X-MC-Unique: U8D4NsYRMluEvww3yfdbCw-1 Received: by mail-wm1-f69.google.com with SMTP id j5so1095298wmi.4 for ; Wed, 06 May 2020 04:57:45 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to; bh=8SQDFnlIJbT5ua1JOyFwQCxTImV9nf4dY7BK+J1cBSE=; b=dz9V4sajLiddedwCKfh+Aek9P5+kP6zJ4XHcgyL+UGJ2WX0YKs34HCV+fVqHIrpyDK 85AuKDmb3lvPDA901znzqKP+9y+wGpY6bmnrwz6BzYr3YlIW1S6FPKt56YpWT3eZCXLs 0Usvt78DTQm0Xcd1dtbEa0/v3v/BjpWLMVmd7BU86w2pPp51DVEJ8Wx2GhMQ5DPgA3Je 6tgqH3thvDIShB52H303sq7IZGhLHnw8WdAbGselYdSQ4TC5WZDTv7ZbhsYYwEyHtRS5 cUQMlRn05KYXfevLBwjVhHecrN+DJIjP54Vydpwsh1K6wA/Jk2U8i4xUXY2ScmuMcVd5 kY7Q== X-Gm-Message-State: AGi0PuacBALgiKG0E/42b9nlFE/zg4WyCphJNaFs2joQ4ULuh0ExWdNs 6hDvSgRAc367IAN64TjaAoM+MRBXs/PdYyuDpBhGl3AhECNBLqMCRqPsfCRdGTdz6QWCGexglm0 LsXl15nDZ8jYlGF5T X-Received: by 2002:a05:600c:2210:: with SMTP id z16mr4188079wml.151.1588766264429; Wed, 06 May 2020 04:57:44 -0700 (PDT) X-Google-Smtp-Source: APiQypKgPL6Idtx8YS8ZSPniHEZVsgz6k4KI77A+1MaVArInKjm4b6YSX9fRi88QPhdunVwvyGecRg== X-Received: by 2002:a05:600c:2210:: with SMTP id z16mr4188044wml.151.1588766264058; Wed, 06 May 2020 04:57:44 -0700 (PDT) Received: from redhat.com (bzq-109-66-7-121.red.bezeqint.net. [109.66.7.121]) by smtp.gmail.com with ESMTPSA id a139sm1060804wme.18.2020.05.06.04.57.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 06 May 2020 04:57:43 -0700 (PDT) Date: Wed, 6 May 2020 07:57:41 -0400 From: "Michael S. Tsirkin" To: Jason Wang Cc: virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, Jesper Dangaard Brouer , Eugenio Perez Martin Subject: Re: performance bug in virtio net xdp Message-ID: <20200506075719-mutt-send-email-mst@kernel.org> References: <20200506035704-mutt-send-email-mst@kernel.org> <7d801479-5572-0031-b306-a735ca4ce0e4@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <7d801479-5572-0031-b306-a735ca4ce0e4@redhat.com> Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, May 06, 2020 at 04:37:41PM +0800, Jason Wang wrote: > > On 2020/5/6 下午4:08, Michael S. Tsirkin wrote: > > So for mergeable bufs, we use ewma machinery to guess the correct buffer > > size. If we don't guess correctly, XDP has to do aggressive copies. > > > > Problem is, xdp paths do not update the ewma at all, except > > sometimes with XDP_PASS. So whatever we happen to have > > before we attach XDP, will mostly stay around. > > > It looks ok to me since we always use PAGE_SIZE when XDP is enabled in > get_mergeable_buf_len()? > > Thanks > Oh right. Good point! Answered in another thread. > > > > The fix is probably to update ewma unconditionally. > >