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Re: Consensus: Tuning runtime behaviour with environment variables.
- From: Alexandre Oliva <aoliva at redhat dot com>
- To: Rich Felker <dalias at aerifal dot cx>
- Cc: libc-alpha at sourceware dot org
- Date: Sun, 02 Jun 2013 14:04:32 -0300
- Subject: Re: Consensus: Tuning runtime behaviour with environment variables.
- References: <51A58A92 dot 4050508 at redhat dot com> <20130529055518 dot GA23030 at domone dot kolej dot mff dot cuni dot cz> <ormwraq3rx dot fsf at livre dot home> <20130601031151 dot GK20323 at brightrain dot aerifal dot cx> <ora9n9i3jc dot fsf at livre dot home> <20130602154150 dot GN20323 at brightrain dot aerifal dot cx>
On Jun 2, 2013, Rich Felker <dalias@aerifal.cx> wrote:
> Do you have any performance figures to justify this?
Sure, in the paper. It also explains the optimization you seem to have
missed, that enables the dynamic loader to turn dynamic TLS into
something very close to initial exec when the TLS segment of a dlopened
library fits in the static TLS segment. I say you seem to have missed
that because you can't possibly be saying that all the work done by
__tls_get_addr() is as costly as simply returning the value passed in in
the correct register, that happens to be precomputed TLS offset. The
shrink-wrapping of __tls_get_addr for the unfortunate cases in which the
TLS segment didn't fit is just a small added benefit.
--
Alexandre Oliva, freedom fighter http://FSFLA.org/~lxoliva/
You must be the change you wish to see in the world. -- Gandhi
Be Free! -- http://FSFLA.org/ FSF Latin America board member
Free Software Evangelist Red Hat Brazil Compiler Engineer