From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-x236.google.com (mail-wr0-x236.google.com [IPv6:2a00:1450:400c:c0c::236]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id A2A2C3B2A4 for ; Thu, 30 Nov 2017 10:57:29 -0500 (EST) Received: by mail-wr0-x236.google.com with SMTP id k61so7087286wrc.4 for ; Thu, 30 Nov 2017 07:57:29 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=C50ZOc1/vxJB1HyLDO3aN4aUajKiVPC8iChTIM1+K8Y=; b=U8sbbRoniX7HyZq0YggQmy1TDUJ6jQY3hYMWMi7GQwDlOwaGw726NtbKcIIQpa1BkZ T8+kZr/N0DeXvpMghPZzh9s1u/jtFrziE/FTfYaBBfpL/+mFUppTGyfbNoJmy1pE3A7L w+1M2NE31S1sBFayUIsnhkvxvjt4QLuj+XN0EVdl8pTOb9pwLhDhpmeZdwbGLgeRvLxq t33JBdjel3n1uj/RcOND1AP7r0DNuZmgCDrywYZDH7fLJd3oR8d7iQMH0N6FyYIMAG7M WxFJzTHJHNAntMpi0Ps6EMpN5PBqqV+FzBB/XgBtsbpS36MukvncYSYnJ/XyEdmzcDsn 6RCg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=C50ZOc1/vxJB1HyLDO3aN4aUajKiVPC8iChTIM1+K8Y=; b=Ew/VzbjdF8HlKRWg5lb7rvn0iNJxSEA+IRIoOluq7TN8yF/VFoui0DlaudmCAV6e1a hAXWZPjIF78zq50HlZTtDtdUIFY23K3WqNJiJTczo1roDDn1fxNZ6jj9WJq9738cfvqw FdZCuAPqqhDfJz1NacYJeTkc9DlLCT0Q9e3Av1AXc0fuSLr8y4WuxL+2GieEkzz0uGWX T9LjFvG7eyGvFAx4U9DEoB1lbm+2Mx/+RGIygRdfYVd2IQRHtNxEUdoBr3oN6LRW3wAN iLRGmCBWNeCMAPuLIu7LxB0WforkGVT9HzJB1RtmlJs1JOgsjg0KVKft/WYtxmtHtnia /z7w== X-Gm-Message-State: AJaThX74lduNTdcZeG8FQ1e2LWGBg1cBRmw/4G+xUVWzMjuVl/Ywi6FK xbv/zo6yEwfl6fplOpxdJ9mO/KwEFDIyEhW507nO8w== X-Google-Smtp-Source: AGs4zMYmBi+Cdpxb8docl2vaJ+K7mfgh4dXu0oqOdRNZwoA4Xif64tnMR19GRoZ9pxwg/K6PFkTJR9mdXmB8XmiXFmc= X-Received: by 10.223.139.8 with SMTP id n8mr2271434wra.225.1512057448454; Thu, 30 Nov 2017 07:57:28 -0800 (PST) MIME-Version: 1.0 Received: by 10.28.203.140 with HTTP; Thu, 30 Nov 2017 07:57:07 -0800 (PST) In-Reply-To: <1512057319.19682.16.camel@gmail.com> References: <4D0E907C-E15D-437C-B6F7-FF348346D615@gmx.de> <7B92DF4D-B6B5-4A64-9E10-119DCA2D4A6F@ifi.uio.no> <1512037480.19682.10.camel@gmail.com> <1512057319.19682.16.camel@gmail.com> From: Neal Cardwell Date: Thu, 30 Nov 2017 10:57:07 -0500 Message-ID: To: Eric Dumazet Cc: Jonathan Morton , Michael Welzl , David Ros , bloat , Yuchung Cheng , Wei Wang Content-Type: multipart/alternative; boundary="f403045e9fb81929af055f354fa3" Subject: Re: [Bloat] benefits of ack filtering X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 30 Nov 2017 15:57:29 -0000 --f403045e9fb81929af055f354fa3 Content-Type: text/plain; charset="UTF-8" On Thu, Nov 30, 2017 at 10:55 AM, Eric Dumazet wrote: > On Thu, 2017-11-30 at 09:51 -0500, Neal Cardwell wrote: > > On Thu, Nov 30, 2017 at 5:24 AM, Eric Dumazet > > wrote: > > > I agree that TCP itself should generate ACK smarter, on receivers > > > that > > > are lacking GRO. (TCP sends at most one ACK per GRO packets, that > > > is > > > why we did not feel an urgent need for better ACK generation) > > > > > > It is actually difficult task, because it might need an additional > > > timer, and we were reluctant adding extra complexity for that. > > > > How about just using the existing delayed ACK timer, and just making > > the delayed ACK logic a bit smarter? We could try using the existing > > logic and timers, but using something adaptive instead of the magic > > "2" MSS received to force an ACK. > > Keep in mind some distros have HZ=250 or even HZ=100 > > So even a 'one jiffie' timer could add 10ms delay. > Right, good point. I forgot about those cases. :-) neal --f403045e9fb81929af055f354fa3 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable


On Thu, Nov 30, 2017 at 10:55 AM, Eric Dumazet <eric.dumazet@gmai= l.com> wrote:
On Thu, 2017-11-30 at 09:51 -0500, Neal Cardwell wrote:
> On Thu, Nov 30, 2017 at 5:24 AM, Eric Dumazet <eric.dumazet@gmail.com
> > wrote:
> > I agree that TCP itself should generate ACK smarter, on receivers=
> > that
> > are lacking GRO. (TCP sends at most one ACK per GRO packets, that=
> > is
> > why we did not feel an urgent need for better ACK generation)
> >
> > It is actually difficult task, because it might need an additiona= l
> > timer, and we were reluctant adding extra complexity for that. >
> How about just using the existing delayed ACK timer, and just making > the delayed ACK logic a bit smarter? We could try using the existing > logic and timers, but using something adaptive instead of the magic > "2" MSS received to force an ACK.

Keep in mind some distros have HZ=3D250 or even HZ=3D100

So even a 'one jiffie' timer could add 10ms delay.
=

Right, good point. I forgot about those cases. :-)

neal


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