From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ob0-x236.google.com (mail-ob0-x236.google.com [IPv6:2607:f8b0:4003:c01::236]) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by huchra.bufferbloat.net (Postfix) with ESMTPS id CDCCB21F33F for ; Thu, 4 Dec 2014 17:11:38 -0800 (PST) Received: by mail-ob0-f182.google.com with SMTP id wo20so7009525obc.13 for ; Thu, 04 Dec 2014 17:11:37 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type:content-transfer-encoding; bh=eu+RhI80EmrkDQBNccO5kh9+/JKftFFbRlrtEMETXzY=; b=FYY0G7g9fpN8QGjztY+iMEzv4x5uQG23Fm2T3bJwQbkkL088X3gBAoDpdgCyqdlK77 OjhaxZwU+dEqFvaJb+5dlnJHIqgg3vuQ/6pvBF3h0JJKbtgTraRxZ7F+8HKtJsY+CF6M QZhGDLMMD2vG65n4esuQJu2AglakQ2PUSioRZPZz1xhdif1E4+g3hNS1I9Ti5bslbhRL mPOcWJWlgkS6yR8MAuZGzqEiExGSIHql44c8ksjM2DyjzhDtn7n4wYMehbs8jM1cBFa1 MfKsuPWQ4Z40tB1JPoeD+fQlgwtQu32jjm7mie8cQNq5IwC7fx/p1HQQqdZzHmInmQyy 15oA== MIME-Version: 1.0 X-Received: by 10.202.171.85 with SMTP id u82mr8461169oie.24.1417741897620; Thu, 04 Dec 2014 17:11:37 -0800 (PST) Received: by 10.202.227.77 with HTTP; Thu, 4 Dec 2014 17:11:37 -0800 (PST) In-Reply-To: <1417738429.22424.29.camel@edumazet-glaptop2.roam.corp.google.com> References: <1417738429.22424.29.camel@edumazet-glaptop2.roam.corp.google.com> Date: Thu, 4 Dec 2014 17:11:37 -0800 Message-ID: From: Dave Taht To: bloat , "aqm@ietf.org" Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Subject: [Bloat] Fwd: [PATCH net-next 2/2] tcp_cubic: refine Hystart delay threshold X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 05 Dec 2014 01:12:07 -0000 fixing hystart at longer rtts with fq + pacing... ---------- Forwarded message ---------- From: Eric Dumazet Date: Thu, Dec 4, 2014 at 4:13 PM Subject: [PATCH net-next 2/2] tcp_cubic: refine Hystart delay threshold To: David Miller Cc: netdev , Nandita Dukkipati , Neal Cardwell , Yuchung Cheng , Sangtae Ha From: Eric Dumazet In commit 2b4636a5f8ca ("tcp_cubic: make the delay threshold of HyStart less sensitive"), HYSTART_DELAY_MIN was changed to 4 ms. The remaining problem is that using delay_min + (delay_min/16) as the threshold is too sensitive. 6.25 % of variation is too small for rtt above 60 ms, which are not uncommon. Lets use 12.5 % instead (delay_min + (delay_min/8)) Tested: 80 ms RTT between peers, FQ/pacing packet scheduler on sender. 10 bulk transfers of 10 seconds : nstat >/dev/null for i in `seq 1 10` do netperf -H remote -- -k THROUGHPUT | grep THROUGHPUT done nstat | grep Hystart With the 6.25 % threshold : THROUGHPUT=3D20.66 THROUGHPUT=3D249.38 THROUGHPUT=3D254.10 THROUGHPUT=3D14.94 THROUGHPUT=3D251.92 THROUGHPUT=3D237.73 THROUGHPUT=3D19.18 THROUGHPUT=3D252.89 THROUGHPUT=3D21.32 THROUGHPUT=3D15.58 TcpExtTCPHystartTrainDetect 2 0.0 TcpExtTCPHystartTrainCwnd 4756 0.0 TcpExtTCPHystartDelayDetect 5 0.0 TcpExtTCPHystartDelayCwnd 180 0.0 With the 12.5 % threshold THROUGHPUT=3D251.09 THROUGHPUT=3D247.46 THROUGHPUT=3D250.92 THROUGHPUT=3D248.91 THROUGHPUT=3D250.88 THROUGHPUT=3D249.84 THROUGHPUT=3D250.51 THROUGHPUT=3D254.15 THROUGHPUT=3D250.62 THROUGHPUT=3D250.89 TcpExtTCPHystartTrainDetect 1 0.0 TcpExtTCPHystartTrainCwnd 3175 0.0 Signed-off-by: Eric Dumazet --- net/ipv4/tcp_cubic.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/ipv4/tcp_cubic.c b/net/ipv4/tcp_cubic.c index c1d07c7ed03d7d37fa28d1509093e686f78134d2..6b6002416a73950d493661ea145= 9870f49917efc 100644 --- a/net/ipv4/tcp_cubic.c +++ b/net/ipv4/tcp_cubic.c @@ -393,7 +393,7 @@ static void hystart_update(struct sock *sk, u32 delay) ca->sample_cnt++; } else { if (ca->curr_rtt > ca->delay_min + - HYSTART_DELAY_THRESH(ca->delay_min>>4)) { + HYSTART_DELAY_THRESH(ca->delay_min >> 3)) { ca->found |=3D HYSTART_DELAY; NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHYSTARTDELAYDETECT); -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html --=20 Dave T=C3=A4ht thttp://www.bufferbloat.net/projects/bloat/wiki/Upcoming_Talks