Re: parallelizing more actions

[Efraim Flashner <efraim@flashner.co.il>]

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On Sat, Nov 11, 2017 at 12:25:01PM +0100, Ludovic Courtès wrote:
> Hi Efraim,
> 
> Efraim Flashner <efraim@flashner.co.il> skribis:
> 
> > While rebuilding glibc-final on aarch64 I realized that the 'strip phase
> > took 235 seconds. The relevant code for 'strip from gnu-build-system is
> > in guix/build/gnu-build-system.scm, starting at line 340, with the
> > actual stripping starting at 398. When I changed 'for-each' to
> > 'par-for-each' the time dropped from 235 seconds to 215, about an 8.5%
> > savings. I'm pretty sure most of that time was spent failing to strip
> > certain files, but it is still a savings.
> 
> Is it on a spinning hard disk or an SSD?  My guess is that most of the
> time is I/O, and that parallelizing doesn’t buy us much (indeed, 8.5% is
> not that much, far from a linear speedup.) 
> 

It was on eMMC, so basically an SSD.

> So I’m mildly reluctant to parallelizing this particular piece of code.
> 
> Thanks,
> Ludo’.

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