Re: [patch] tls-2.5.31-C3

Ingo Molnar
2002-08-12T13:57:10Z

On 12 Aug 2002, Luca Barbieri wrote:

> > > Numbers:
> > > unconditional copy of 2 tls descs: 5 cycles
> > > this patch with 1 tls desc: 26 cycles
> > > this patch with 8 tls descs: 52 cycles
> >
> > [ 0 tls descs: 2 cycles. ]
> Yes but common multithreaded applications will have at least 1 for
> pthreads.

i would not say 'common' and 'multithreaded' in the same sentence. It
might be so in the future, but it isnt today.

> > how did you calculate this?
> ((26 - 5) / 2000) * 100 ~= 1
> Benchmarks done in kernel mode (2.4.18) with interrupts disabled on a
> Pentium3 running the rdtsc timed benchmark in a loop 1 million times
> with 8 unbenchmarked iterations to warm up caches and with the time to
> execute an empty benchmark subtracted.

old libpthreads or new one?

> > glibc multithreaded applications can avoid the
> > lldt via using the TLS, and thus it's a net win.
> Surely, this patch is better than the old LDT method but much worse than
> the 2-TLS one.

people asked for a 3rd TLS already.

Ingo