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([2620:15c:2c1:200:55c7:81e6:c7d8:94b]) by smtp.gmail.com with ESMTPSA id e16sm7577660pgk.77.2020.01.24.15.49.16 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 24 Jan 2020 15:49:17 -0800 (PST) Subject: Re: debugging TCP stalls on high-speed wifi To: Johannes Berg , Krishna Chaitanya Cc: Neal Cardwell , =?UTF-8?Q?Toke_H=c3=b8iland-J=c3=b8rgensen?= , linux-wireless , Netdev References: <14cedbb9300f887fecc399ebcdb70c153955f876.camel@sipsolutions.net> <99748db5-7898-534b-d407-ed819f07f939@gmail.com> From: Eric Dumazet Message-ID: <9f984cda-2209-fa07-569e-2555ef2aa78d@gmail.com> Date: Fri, 24 Jan 2020 15:49:15 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-wireless-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org On 1/24/20 2:34 AM, Johannes Berg wrote: > On Fri, 2019-12-13 at 14:40 +0530, Krishna Chaitanya wrote: >> >> Maybe try 'reno' instead of 'cubic' to see if congestion control is >> being too careful? > > I played around with this a bit now, but apart from a few outliers, the > congestion control algorithm doesn't have much effect. The outliers are > > * vegas with ~120 Mbps > * nv with ~300 Mbps > * cdg with ~600 Mbps > > All the others from my list (reno cubic bbr bic cdg dctcp highspeed htcp > hybla illinois lp nv scalable vegas veno westwood yeah) are within 50 > Mbps or so from each other (around 1.45Gbps). > When the stalls happens, what is causing TCP to resume the xmit ? Some tcpdump traces could help. (-s 100 to only capture headers)