X-Recipient: archive-cygwin@delorie.com X-SWARE-Spam-Status: No, hits=-0.8 required=5.0 tests=AWL,BAYES_50 X-Spam-Check-By: sourceware.org Date: Tue, 30 Jun 2009 14:23:41 -0500 From: Brian Ford Reply-To: cygwin@cygwin.com To: cygwin@cygwin.com Subject: Re: Call for TESTING (was Re: [1.7.0-50] scp progress counter flies through first 175 MB or so) In-Reply-To: <4A4A3B64.4030004@etr-usa.com> Message-ID: References: <20090625101039.GP7289@calimero.vinschen.de> <20090625140508.GA17040@ednor.casa.cgf.cx> <20090625143651.GR7289@calimero.vinschen.de> <20090625145005.GB18338@ednor.casa.cgf.cx> <20090628193155.GA10407@ednor.casa.cgf.cx> <20090629092857.GZ30864@calimero.vinschen.de> <20090629095322.GD30864@calimero.vinschen.de> <20090629142348.GB19123@ednor.casa.cgf.cx> <20090629144030.GC19123@ednor.casa.cgf.cx> <4A490F0E.6040806@etr-usa.com> <20090630112617.GS30864@calimero.vinschen.de> <4A4A3B64.4030004@etr-usa.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-IsSubscribed: yes Mailing-List: contact cygwin-help@cygwin.com; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: cygwin-owner@cygwin.com Mail-Followup-To: cygwin@cygwin.com Delivered-To: mailing list cygwin@cygwin.com On Tue, 30 Jun 2009, Warren Young wrote: > Corinna Vinschen wrote: > > What's still not clear is why the ssh process takes so much CPU. > > Too many buffer copies? It takes a surprising amount of CPU power to > fill a gigabit pipe from userland. Double or triple that workload with > unnecessary copies, and there goes your transfer rate, evaporating on > the wind. Even more so for context switches ;-): http://www.cygwin.com/ml/cygwin-developers/2007-10/msg00040.html although this performance penalty was removed from read/write and friends: http://www.cygwin.com/ml/cygwin-developers/2007-12/msg00004.html it is still present for send/recv and friends. I'd be happy to make a donation or organize a fund raising effort if it would help to find a work around for this long standing performance issue. -- Brian Ford Staff Realtime Software Engineer VITAL - Visual Simulation Systems FlightSafety International the best safety device in any aircraft is a well-trained crew... -- 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