Re: [PATCH] libtool: minimise forks per invocation on cygwin and mingw.

[Eric Blake]

On 12/08/2011 08:29 AM, Charles Wilson wrote:
> On 12/8/2011 5:21 AM, Gary V. Vaughan wrote:
>> The recently pushed series of patches included the controversial
>> introduction of an additional 3 forks per invocation, which might
>> add a minute or two of wall-clock time to giant builds on windows.
>> By assuming that windows will run shell scripts on some shell with
>> all the modern optional features that libtool wants, this patch
>> eliminates even those 3 new forks.
>>
>> Okay to push?
> 
> Has anybody done a comparison between:
> 
> cygwin + libtool + dash/posh (e.g. small, fast shell -- without XSI)

Umm, dash has XSI features (where XSI features covers things like
${var##prefix}).  It is only shells like Solaris /bin/sh that lack this
mandatory POSIX feature.  Meanwhile, libtool is using more than just XSI
extensions; for example, it is probing for bash's += variable append
extension.  I'm not sure how much difference += makes (especially since
it is not shaving on forks, but is reducing O(n^2) malloc behavior for
large piece-wise constructions), but do know that XSI variable usage
definitely shaves a lot of forkes.

As for actual timing comparisons, I have not done any recently.

-- 
Eric Blake   address@hidden    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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