Re: Add a cooperative FS lock to lilypond-book. (issue 555360043 by address@hidden)

[hanwenn]

On 2020/02/23 16:05:08, dak wrote:
> On 2020/02/23 15:54:54, hanwenn wrote:
> > I think this is worth it because it simplifies the build system, and
puts the
> > locking in the place where we actually access the resource.
> 
> Is there any indication that letting Make run multiple instances of
> lilypond-book with every instance except one at a time locking up is
going to be
> a net win for performance?

input/regression/lilypond-book:

rm -rf out-tst; time make out=tst local-test -j4 CPU_COUNT=4


before
real    1m16.588s

after
real    0m25.224s


> I still don't see what this is supposed to buy us over using
CPU_COUNTS for
> invoking parallel LilyPond instances.  In particular since the
parallel LilyPond
> instances are forked off at a time when LilyPond has completed its
startup, and
> in the context of the current Guile-v2 integration, startup times are
relevant. 
> Even though considering the number of files processed in one LilyPond
process,
> their overall impact should still be comparatively confined.

The problem is that several other things are serialized in the build
because of lilypond-book.

I used fcntl locking which impervious to stale locks (exiting a process
drops locks automatically)


https://codereview.appspot.com/555360043/