Fast sigblock (AKA rtld speedup)

[Konstantin Belousov]

On Sat, Jan 12, 2013 at 12:51:56AM +0400, Lev Serebryakov wrote:
> Hello, Konstantin.
> You wrote 11 января 2013 г., 13:54:59:
> 
> 
> KB> http://people.freebsd.org/~kib/misc/rtld-sigblock.2.patch
> KB> is the commit candidate. Now kernel informs rtld about supprt for
>  Is  it  first  patch  in  this state, which implements idea of shared
>  memory between kernel and userland to spped up some syscalls? There
>  were discussions about this approach for speedup of
>  getpid()/getppid()/gettimeofday(), but without code ready for commit,
>  am I right?

No, you are wrong.

FreeBSD have shared page for very long time, and it is used for syscall-less
gettimeofday for quite some time.

Non-shared page which could carry per-thread or per-process information,
neccessary for looking good in the trivial benchmarks, like getpid(),
is different case.

The patch does not implement the idea of speeding up some syscalls at all.
It provides the special purpose one-off implementation of the alternate
mechanism, for the internal consumption of rtld.
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