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:from:to:subject:date:message-id:references
	:in-reply-to:content-type:content-id:content-transfer-encoding
	:mime-version; q=dns; s=default; b=qHtaTSdjDpGFOZjlW62BUVm5U1Pic
	8+MaY3cneGFE+uausgIbdZ+3HWLye6CdeGmiSE4riJhcRis5WmqvMM5DUreobt2y
	7H9zQxEW9HKYXl+QYp8BsiS2gwWUo3UuyFT5gnnYRXqfOnRj8skHQJgL2WaWoBKo
	gz/AFsM9FmsaCY=
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:from:to:subject:date:message-id:references
	:in-reply-to:content-type:content-id:content-transfer-encoding
	:mime-version; s=default; bh=TurAOi1uawatZ3IZK4GFgmj6pcs=; b=ADs
	T8hlEHpU976imguGQtUJo2ENmvgD13MsL7K9TcXsyPxoMaP+ulYoHHX4Tp9XS/0J
	dNTrB5yqKwbub/Qb2gmSe/naI2tmwPZJaPkBa06vt6RFS0xdRQa9HAWdaou72ViJ
	W6exVqJ2R/AiIUjNkZwSfXdEc6lUtwi6xRBK0IrE=
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-Spam-SWARE-Status:	No, score=-1.9 required=5.0 tests=BAYES_00,MIME_BASE64_BLANKS,RCVD_IN_DNSWL_NONE,SPF_HELO_PASS,SPF_PASS autolearn=ham version=3.3.2 spammy=timer, waits, Hx-languages-length:1609, respond
X-HELO:	NAM02-BL2-obe.outbound.protection.outlook.com
DKIM-Signature:	v=1; a=rsa-sha256; c=relaxed/relaxed; d=cornell.edu; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=WImcm0HmVnPTlSKQjr1UhUJZZIP5xoLy8T2wj/NXQpc=; b=KrLTzdEU5uWLriYGPyE88X+9BUBL4qXQq0hAzzeudidalzLwxVLEbwJaQjr594IIRWp2fKI104OJKWwLoQaIRE+mmeJcvwPJDB/1dqnQv+783NF3AmHYKf5RkAz14tKORqzqWaWqyk70fk6OxXu9+UDC3VhRo7kJiELi54Stk2I=
From:	Ken Brown <kbrown AT cornell DOT edu>
To:	"cygwin AT cygwin DOT com" <cygwin AT cygwin DOT com>
Subject:	Re: The timerfd functions slow down emacs
Date:	Sat, 23 Feb 2019 16:05:03 +0000
Message-ID:	<1df3d7ce-1427-cbd4-0978-7236b1903440@cornell.edu>
References:	<04048cc3-091a-b55c-372b-bde29273d952 AT cornell DOT edu>
In-Reply-To:	<04048cc3-091a-b55c-372b-bde29273d952@cornell.edu>
user-agent:	Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.5.0
authentication-results:	spf=none (sender IP is ) smtp.mailfrom=kbrown AT cornell DOT edu;
received-spf:	None (protection.outlook.com: cornell.edu does not designate permitted sender hosts)
x-ms-exchange-senderadcheck:	1
MIME-Version:	1.0
X-MS-Exchange-CrossTenant-mailboxtype:	HOSTED
X-IsSubscribed:	yes
X-MIME-Autoconverted:	from base64 to 8bit by delorie.com id x1NG5j4w004526

On 2/21/2019 6:52 PM, Ken Brown wrote:
> When emacs is built, it detects the timerfd functions and uses them if they're
> found.  Now that Cygwin has these functions, the resulting build of emacs is
> very slow to respond to user input.  If I press a key, there is a 1-2 second
> delay before emacs responds.
> 
> I can work around this by configuring emacs with emacs_cv_have_timerfd=no, but
> it would be nice to find the cause.  I'll try to make an STC, but I thought I'd
> report it here in the meantime, in case anyone has ideas or debugging suggestions.

I don't have an STC yet, but if I start emacs and then attach gdb to it at 
random times, the backtrace always look like this:

#0  0x00007ffbb192b4f4 in ntdll!ZwWaitForMultipleObjects ()
    from /c/WINDOWS/SYSTEM32/ntdll.dll
#1  0x00007ffbadf56099 in WaitForMultipleObjectsEx ()
    from /c/WINDOWS/System32/KERNELBASE.dll''
#2  0x00007ffbadf55f8e in WaitForMultipleObjects ()
    from /c/WINDOWS/System32/KERNELBASE.dll
#3  0x0000000180159f9d in timerfd_tracker::wait (this=this AT entry=0x1803a22c0,
     nonblocking=false)
     at /usr/src/debug/cygwin-3.0.1-1/winsup/cygwin/timerfd.cc:448
#4  0x00000001800a7b0e in fhandler_timerfd::read (this=<optimized out>,
     ptr=0xffffba30, len=@0xffffb9b0: 8)
     at /usr/src/debug/cygwin-3.0.1-1/winsup/cygwin/fhandler_timerfd.cc:134
[...]

This suggests to me that the slowdown comes from timerfd_tracker::wait.

The context is that emacs creates a timerfd timer that expires every 2 seconds, 
'select' waits for the timer's file descriptor to be ready for reading, and then 
emacs calls 'read'.

Ken

--
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

- Raw text -