X-Recipient: archive-cygwin AT delorie DOT com DomainKey-Signature: a=rsa-sha1; c=nofws; d=sourceware.org; h=list-id :list-unsubscribe:list-subscribe:list-archive:list-post :list-help:sender:subject:references:to:from:reply-to:message-id :date:mime-version:in-reply-to:content-type :content-transfer-encoding; q=dns; s=default; b=b345yjtONcgfO9Uw mnzsSRtSyoS9AL3EX0AwRnNqkSJ5toQG3x/kBOybfr7A7uGH2SxZHK4/QzWp6UAN hYDTMus342HEZgBrTuTdo6DHye3BM0WG1IqAGGOhKo3tyR70BV6h4zcVSD4w3GOZ bEG+Z5PJOfLUBNlUyKot64Ddsx4= DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=sourceware.org; h=list-id :list-unsubscribe:list-subscribe:list-archive:list-post :list-help:sender:subject:references:to:from:reply-to:message-id :date:mime-version:in-reply-to:content-type :content-transfer-encoding; s=default; bh=6d1XkDxV8H+a0rSKOmPVvP LgWHE=; b=WkN5I5d4kbgq5ampZ0j6NSH2OKVFtxs6kZySM35teMe13DtQYAsjbY Byv5jGDzANNBRxU1S0oGMXS1EES0yhnoXg6piSNvu6+tDTNXzbuWX+LXX4v/6Wdb NiLn/Ajv38e7SbNsXOxcQfL01vuQdrfLjCNY4FGp8ej5cuq5eJas4= Mailing-List: contact cygwin-help AT cygwin DOT com; run by ezmlm List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: cygwin-owner AT cygwin DOT com Mail-Followup-To: cygwin AT cygwin DOT com Delivered-To: mailing list cygwin AT cygwin DOT com Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=0.3 required=5.0 tests=AWL,BAYES_20,KAM_LAZY_DOMAIN_SECURITY,RCVD_IN_DNSWL_LOW autolearn=no version=3.3.2 spammy=Hx-spam-relays-external:shaw.ca, H*r:shaw.ca, H*RU:shaw.ca, Hx-spam-relays-external:!192.168.1.100! X-HELO: smtp-out-no.shaw.ca X-Authority-Analysis: v=2.2 cv=XqWKARN9 c=1 sm=1 tr=0 a=WqCeCkldcEjBO3QZneQsCg==:117 a=WqCeCkldcEjBO3QZneQsCg==:17 a=IkcTkHD0fZMA:10 a=w_pzkKWiAAAA:8 a=J1_jgBw0DZDVExNvRqgA:9 a=QEXdDO2ut3YA:10 a=buB1NfXUTBUA:10 a=sRI3_1zDfAgwuvI8zelB:22 Subject: Re: Cygwin TCP slow References: To: cygwin AT cygwin DOT com From: Brian Inglis Reply-To: Brian DOT Inglis AT SystematicSw DOT ab DOT ca Message-ID: <5adc37f5-608b-6c1f-6d14-83343c82dc9f@SystematicSw.ab.ca> Date: Mon, 28 Nov 2016 13:51:03 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-CMAE-Envelope: MS4wfHdmAIqVP/PCaaWKNp9m7LVxRBIZi4H5zUnAiLBI6vGH19Q5c0P2pO9a6qi7TDrsDvqYElnlCZ5po9TzC5V6Fubb0zNKgxX2DXQEoZM4k0/maKxPXDCM iE9wzG53D61n/k7wVZXZjjQLJgYjl4lf7hmKhYXFN4XnE0VIK1BnJmhYFBzQFy3i/7lonUOeqYk7Qw== X-IsSubscribed: yes On 2016-11-28 12:54, Daniel Havey wrote: > We have had complaints from several large hardware vendors that > Windows networking is slow for apps like iperf that are used to > measure throughput. Iperf on Windows is compiled against the > cygwin1.dll. We have root caused the problem to a couple of lines of > code in net.cc that set SO_RCVBUF and SO_SNDBUF to about 200KB. > > The theoretical window/RTT plot for the buffer size set by Cygwin > (0x34000 = 200KB) gives us: > 1ms -> 1703Mbps > 2ms -> 851Mbps > 3ms -> 567Mbps > 4ms -> 425Mbps > 5ms -> 340Mbps > 6ms -> 283Mbps > 7ms -> 243Mbps > 8ms -> 212Mbps > 9ms -> 189Mbps > 10ms -> 170Mbps > 20ms -> 85Mbps > 40ms -> 42Mbps > 60ms -> 28Mbps > 80ms -> 21Mbps > > We have confirmed this by experiment and also confirmed that the > limitation goes away if the buffers are not manually set. Windows has > autotuning and when the buffers are set manually the autotuning is > disabled. This is causing the throughput limitation. So we would > like to formally ask that you please not manually set SO_RCVBUF or > SO_SNDBUF. See problem reports: http://cygwin.com/problems.html Provide STC, patches, attach cygcheck -svr output? Links to downstream bug reports, testing, results? Note that Cygwin iperf is year old 2.0.5. -- Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple