Re: dfa MT-safe?

[arnold]

Hi.

Bruno Haible <address@hidden> wrote:

> > In any case, gawk's use of it is (and will remain) single-threaded.
> > It'd be nice if your fix did not pull in more libraries, like libpthread
> > or whatever, since that would considerably complicate things for me,
> > for no actual gain w.r.t. gawk.
>
> If you add these two lines to configure.ac:
>   gl_cv_func_setlocale_null_all_mtsafe=yes
>   gl_cv_func_setlocale_null_one_mtsafe=yes
> no additional libraries will be needed.

How? I don't use gnulib in gawk.

> > I'm curious what is the use case for multithreaded dfa?
>
> One could speed up
>   grep -r PATTERN DIRECTORY_WITH_MANY_FILES
> by a large factor (probably 4x or 5x, on a CPU with 8 threads).
> This would be done by modifying 'grep' to process each file in a
> separate thread. The kernel can feed the data of these files to 'grep'
> in parallel. Only the output phase needs to serialize things.

I suspect that exactly because of the output phase you won't see
such a huge speedup in practice, but it's worth a shot.

On the assumption that setlocale is the only blocker, I would rather
see an additional `char *locale_name' parameter added to dfa_syntax.
That way the caller can get the value and pass it in, and the
dfa code becomes mt-safe at next to no cost.

Thanks,

Arnold