bug#23269: Multi-threaded operation, mbrtowc, and "untangle" script [was Re: bug#23269...]

[Zev Weiss]

On Thu, Apr 21, 2016 at 07:43:29AM -0700, Paul Eggert wrote:
> On 04/21/2016 02:55 AM, address@hidden wrote:
> > it
> > would be a very suprising change in behavior if output from multiple
> > files comes out interleaved, instead of in the order the files were
> > specified on the command line.
>
> I presume that computation is interleaved but the output order is the 
> same as before, unless the user specifies an option saying speed 
> trumps predictability.

For what it's worth, the command-line flag added by my multithreading 
patch series as it currently stands is pretty much that (speed over 
predictability).  In the interest of simplicity, it omits per-file 
output buffering and just outputs matching lines as they are found -- 
the non-determinism this introduces into its output is the reason it's 
left as an opt-in command-line flag and not on by default.

[Strictly speaking even in the default "single-threaded" mode it *is* in 
fact actually multi-threaded, but there's only one search thread, so 
output ordering is unaffected.  In theory even this could allow a slight 
performance improvement by overlapping pattern-matching with directory 
traversal and prefetching in the master thread, but I'd guess it's 
probably negligible in most cases, and isn't really the goal of the 
patches.]


Zev Weiss