X-Recipient: archive-cygwin@delorie.com X-Spam-Check-By: sourceware.org Date: Wed, 1 Jul 2009 11:26:17 +0200 From: Corinna Vinschen 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) Message-ID: <20090701092617.GU30864@calimero.vinschen.de> Reply-To: cygwin@cygwin.com Mail-Followup-To: cygwin@cygwin.com References: <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 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.19 (2009-02-20) 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 Jun 30 14:23, Brian Ford wrote: > 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. The data is copied only once, from the application buffer to the underlying WinSock socket buffer and vice versa. There's no additional copy of buffer data in Cygwin. > 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 removed the sig_dispatch_pending calls from send/recv and friends. Note, however, that this has no influence on the ssh/scp results we were talking about in this thread. ssh/scp are using read/write calls. Anyway, using ssh/scp with the latest from CVS looks much better now. It doesn't eat up all CPU anymore and the performance looks pretty well as far as I can tell. Corinna -- Corinna Vinschen Please, send mails regarding Cygwin to Cygwin Project Co-Leader cygwin AT cygwin DOT com Red Hat -- 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