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Date: Sun, 13 Jan 2013 14:32:00 +0100
From: Jilles Tjoelker <jilles@stack.nl>
To: Konstantin Belousov <kostikbel@gmail.com>, davidxu@freebsd.org
Subject: Re: Fast sigblock (AKA rtld speedup)
Message-ID: <20130113133159.GA72462@stack.nl>
References: <20130107182235.GA65279@kib.kiev.ua>
 <20130111095459.GZ2561@kib.kiev.ua> <50EFE830.3030500@freebsd.org>
 <20130111204938.GD2561@kib.kiev.ua>
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 <20130112053147.GH2561@kib.kiev.ua>
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On Sat, Jan 12, 2013 at 05:25:47PM +0100, Jilles Tjoelker wrote:
> This suggests a different rather simpler change. Libthr can always use
> its rtld lock implementation instead of only when multiple threads
> exist. This avoids the sigprocmask() syscalls and should not be much
> slower than the default implementation in rtld because that also
> contains atomic operations (both the unpatched and the patched version).
> People that care about performance of exceptions can then link in libthr
> (in many cases, it is already linked in to allow for (the possibility
> of) threading).

> I have tested this and exceptions were indeed more than twice as fast in
> my test program if I created an extra thread doing nothing than in the
> fully single-threaded version (with or without libthr).

Here is a patch. It is lightly tested.

The function _thr_rtld_fini() can be removed afterwards because it is no
longer used.

Index: lib/libthr/thread/thr_init.c
===================================================================
--- lib/libthr/thread/thr_init.c	(revision 244639)
+++ lib/libthr/thread/thr_init.c	(working copy)
@@ -363,6 +363,7 @@
 		_thr_signal_init();
 		if (_thread_event_mask & TD_CREATE)
 			_thr_report_creation(curthread, curthread);
+		_thr_rtld_init();
 	}
 }
 
Index: lib/libthr/thread/thr_kern.c
===================================================================
--- lib/libthr/thread/thr_kern.c	(revision 244639)
+++ lib/libthr/thread/thr_kern.c	(working copy)
@@ -57,11 +57,6 @@
 		return (0);
 
 	__isthreaded = threaded;
-	if (threaded != 0) {
-		_thr_rtld_init();
-	} else {
-		_thr_rtld_fini();
-	}
 	return (0);
 }
 

-- 
Jilles Tjoelker