X-Spam-Check-By: sourceware.org
Message-ID: <4582CA47.2070407@algonet.se>
Date: Fri, 15 Dec 2006 17:16:07 +0100
From: Magnus Holmgren <lear AT algonet DOT se>
User-Agent: Thunderbird 1.5.0.7 (Windows/20060909)
MIME-Version: 1.0
To: cygwin AT cygwin DOT com
Subject: Re: Cygwin slower on one computer
References: <45804D3A DOT 6060602 AT algonet DOT se>
In-Reply-To: <45804D3A.6060602@algonet.se>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
X-Antivirus: avast! (VPS 0659-0, 2006-12-15), Outbound message
X-Antivirus-Status: Clean
X-IsSubscribed: yes
Mailing-List: contact cygwin-help AT cygwin DOT com; run by ezmlm
List-Id: <cygwin.cygwin.com>
List-Subscribe: <mailto:cygwin-subscribe AT cygwin DOT com>
List-Archive: <http://sourceware.org/ml/cygwin/>
List-Post: <mailto:cygwin AT cygwin DOT com>
List-Help: <mailto:cygwin-help AT cygwin DOT com>, <http://sourceware.org/ml/#faqs>
Sender: cygwin-owner AT cygwin DOT com
Mail-Followup-To: cygwin AT cygwin DOT com
Delivered-To: mailing list cygwin AT cygwin DOT com

Magnus Holmgren wrote:

 > I'm trying to figure out why Cygwin build things so much slower on one
 > computer I have. We're talking about more than 3 times slower on a
 > computer that ought to be a bit faster (Athlon64 at 2.2-2.4 GHz,
 > compared to a  Pentium M at 1.8 GHz).

After some more digging - and a bit of feedback off-list - I get the 
feeling (in the cases I've noticed at least) that the speed difference 
is mainly explained by the following reasons (in no particular order):

* fork is expensive.
* vfork is just a wrapper for fork on cygwin.
* fork is much more expensive on AMD than on Intel.

The third one is the one I'm most unsure about, as I only really have 
data about one Intel architecture (the Pentium M). But on the AMD 
system, the page fault delta (as reported by Process Explorer) during a 
build is a little more than 10,000 per second, while on the Intel 
system, the page fault delta can go to 30,000 per second.

(Anyone who knows how SFU implements (v)fork? :)

    Magnus

--
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple
Problem reports:       http://cygwin.com/problems.html
Documentation:         http://cygwin.com/docs.html
FAQ:                   http://cygwin.com/faq/