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:to:references:from:message-id:date
	:mime-version:in-reply-to:content-type
	:content-transfer-encoding; q=dns; s=default; b=Ho+1uB4oaaKjvdEy
	5WdaN5DTW2iCJn0b36BfzFMbUNVwQqBIUSvqUqbLH9qM8pQjLPLi31hcaXVYRVxn
	YxfZVtOcMu3StUx1GZ5xtVV0+2YElI9YhALacJzL+3hyuX9+vhsj8bMvy9y73OjF
	t3txRz0+97AuD/LJizZ1nX3NgY0=
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:to:references:from:message-id:date
	:mime-version:in-reply-to:content-type
	:content-transfer-encoding; s=default; bh=JrFFlNSVuTq2mrFVzJsMQf
	pFEeQ=; b=Cbcm325pF/0o1fA+uoE0IVSbD9Ck3oEtkn9sypb06yK5+wRE8Kq8IX
	lm8xlbClV9RRzT2A2U0NxYEXgZiYuAVz4GeDIU/xrhM6eEgoLgVZhtBXjRGEmpXh
	A9s9nukzmxLOen+ZRME5o6fmiAo5E4sP9HYP4kOIDLNt+P2316HEk=
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
Authentication-Results: sourceware.org; auth=none
X-Virus-Found: No
X-Spam-SWARE-Status: No, score=0.0 required=5.0 tests=AWL,BAYES_50,KAM_LAZY_DOMAIN_SECURITY autolearn=no version=3.3.2
X-HELO: m0.truegem.net
Subject: Re: Cygwin multithreading performance
To: cygwin AT cygwin DOT com
References: <CABPLASTtRK4mNxh0M_AnZgjJQ15kWPx+L=U=VCU3Wwi7jV_57A AT mail DOT gmail DOT com> <564E3017 DOT 90205 AT maxrnd DOT com> <CABPLASTLrH_udLuu2F-m5P6dkENW1Z4YHEudp4NG0-FGLJgPMg AT mail DOT gmail DOT com> <5650379B DOT 4030405 AT maxrnd DOT com> <20151121105301 DOT GE2755 AT calimero DOT vinschen DOT de> <5652C402 DOT 7040006 AT maxrnd DOT com> <24780-1448274431-7444 AT sneakemail DOT com> <5653B52B DOT 5000804 AT maxrnd DOT com> <20151126093427 DOT GJ2755 AT calimero DOT vinschen DOT de> <5656DDEF DOT 9070603 AT maxrnd DOT com> <5662C199 DOT 7040906 AT maxrnd DOT com> <CABPLAST5EnifrAQ2xKZmohKhyxQHh=K3x3DeCL+BTdHN8nN98w AT mail DOT gmail DOT com> <566367C8 DOT 5020703 AT maxrnd DOT com> <CABPLASSY3WWpHAeh=5gqRKdg85M8Wzkrq9qMaDhzhk2zvxgcOw AT mail DOT gmail DOT com>
From: Mark Geisert <mark AT maxrnd DOT com>
Message-ID: <5663EB9A.40002@maxrnd.com>
Date: Sun, 6 Dec 2015 00:02:34 -0800
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:42.0) Gecko/20100101 Firefox/42.0 SeaMonkey/2.39
MIME-Version: 1.0
In-Reply-To: <CABPLASSY3WWpHAeh=5gqRKdg85M8Wzkrq9qMaDhzhk2zvxgcOw@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit

Kacper Michajlow wrote:
> 2015-12-05 23:40 GMT+01:00 Mark Geisert <mark AT maxrnd DOT com>:
>> It looks like we're going to have to compare actual pthread_mutex_lock()
>> implementations.  Inspecting source is nice but I don't want to be chasing a
>> mirage so I really hope there's a pthread_mutex_lock() function inside the
>> MinGW git you are running.  gdb could easily answer that question.  Could
>> you please do an 'info func pthread_mutex_lock' after starting MinGW git
>> under MinGW gdb with a breakpoint at main() (so libraries are loaded).
[...]
> Hmm, thinking about it mingw doesn't have pthread implementation or
> any wrapper for it. If someone needs pthread they would probably go
> for pthreads-w32 implementation.
>
> I started to wonder because I don't recall git would need pthreads to
> compile on Windows. And indeed they have a wrapper for Windows API...
> https://github.com/git/git/blob/master/compat/win32/pthread.h
> https://github.com/git/git/blob/master/compat/win32/pthread.c

OK, so git has its own pthread_mutex_lock/unlock ops which map to very 
light-weight critical section operations.

> Though it is not really a matter that "native" git build is fast and
> all, but that Cygwin's one really struggles if it comes to MT workload.

In the worst cases I see using your testcase, about half the time the 
busiest locks are processed within 1 usec but there's a spectrum of 
longer latencies for the other half of the time.  I don't know (yet) if 
that can be improved in Cygwin's more general implementation but at 
least the matter has now been brought to our attention :).

> And this not only issue with git unfortunately. Download speeds are
> also limited on Cygwin. I know POSIX compatibility layers comes with a
> price but I would love to see improvements in those areas.
> Cygwin:
> Receiving objects: 100% (230458/230458), 78.41 MiB | 1.53 MiB/s, done.
> "native" git:
> Receiving objects: 100% (230458/230458), 78.41 MiB | 18.54 MiB/s, done.

You're asserting this additional testcase has the same cause.  What is 
telling you that?  And FTR what is the git command you are issuing?  I 
can then do the lock latency analysis on this new testcase if warranted.
Thanks,

..mark

--
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