Re: cpuset/affinity interfaces and TSX lock elision in musl

[Szabolcs Nagy <nsz@port70.net>]

* Daniel Cegie?ka <daniel.cegielka@gmail.com> [2013-05-17 09:41:18 +0200]:
> >> 2) The upcoming glibc will have support for TSX lock elision.
> >>
> >> http://en.wikipedia.org/wiki/Transactional_Synchronization_Extensions
> >>
> >> http://lwn.net/Articles/534761/
> >>
> >> Are there any outlook that we can support TSX lock elision in musl?
> >
> > I was involved in the discussions about lock elision on the glibc
> > mailing list, and from what I could gather, it's a pain to implement
> > and whether it brings you any benefit is questionable.
> 
> There is currently no hardware support, so the tests were done in the
> emulator. It's too early to say there's is no performance gain.
> 

it's not the lock performance that's questionable
but the benefits

locks should not be the bottleneck in applications
unless there is too much shared state on hot paths,
which is probably a design bug or a special use-case
for which non-standard synchronization methods may
be better anyway

for the implementation costs check the glibc
discussion where rich pointed out conformance
issues in the original design

http://article.gmane.org/gmane.comp.lib.glibc.alpha/29240