Date: Sun, 13 Jan 2013 15:51:10 +0200 From: Konstantin Belousov <kostikbel@gmail.com> To: Jilles Tjoelker <jilles@stack.nl> Cc: arch@freebsd.org, davidxu@freebsd.org, toolchain@freebsd.org Subject: Re: Fast sigblock (AKA rtld speedup) Message-ID: <20130113135110.GS2561@kib.kiev.ua> In-Reply-To: <20130113133159.GA72462@stack.nl> References: <20130107182235.GA65279@kib.kiev.ua> <20130111095459.GZ2561@kib.kiev.ua> <50EFE830.3030500@freebsd.org> <20130111204938.GD2561@kib.kiev.ua> <20130111232906.GA29017@stack.nl> <20130112053147.GH2561@kib.kiev.ua> <20130112162547.GA54954@stack.nl> <20130113133159.GA72462@stack.nl>
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On Sun, Jan 13, 2013 at 02:32:00PM +0100, Jilles Tjoelker wrote:
> 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).
>=20
> > 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).
>=20
> Here is a patch. It is lightly tested.
>=20
> The function _thr_rtld_fini() can be removed afterwards because it is no
> longer used.
>=20
> Index: lib/libthr/thread/thr_init.c
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> --- 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();
Please add a comment there, describing the reason for initializing
threaded rtld locks.
> }
> }
> =20
> Index: lib/libthr/thread/thr_kern.c
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> --- lib/libthr/thread/thr_kern.c (revision 244639)
> +++ lib/libthr/thread/thr_kern.c (working copy)
> @@ -57,11 +57,6 @@
> return (0);
> =20
> __isthreaded =3D threaded;
> - if (threaded !=3D 0) {
> - _thr_rtld_init();
> - } else {
> - _thr_rtld_fini();
> - }
> return (0);
> }
I do not object.
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