irt: tools/squashfs4: enable parallel builds

[Paul Oranje]

Hi,
See below, regards,
Paul


> Op 3 apr. 2023, om 00:28 heeft Elliott Mitchell <ehem+openwrt at m5p.com> het volgende geschreven:
> 
> Am I the only person who finds commit 3efd49a588
Cannot find that one, but have you seen 82e1f041f9a6cf9232c9f73938ef3b11c34cca0f ?

> ("tools/squashfs4: enable parallel builds") a bit odd?  Specifically from
> the commit message:
> 
>> Run `time make tools/squashfs4/{clean,compile} -j$(nproc)`
>> Before:
>> real    0m8.803s
>> user    0m12.415s
>> sys     0m1.317s
>> After:
>> real    0m13.781s
>> user    0m13.290s
>> sys     0m1.528s
> 
> So a parallel build of squashfs4 took more processor time in user mode,
> more processor time in supervisor mode, and *more* wall clock time?
> 
> More processor time is fine, that comes with coordinating parallel build
> processes.  The goal of parallel builds is to spend a bit of processor
> time to *reduce* wall clock time use.  Yet a parallel build of
> `squashfs4` is stated to have resulted in a 50% increase?
> 
> Uhm.  Perhaps your computer's processor interconnect is very slow?
> Does this computer have an extremely high processor count?  I do note
> `squashfs4` doesn't have very many source files.
> 
> Generally I would support the use of parallel builds, but unless I'm
> missing something this appears the case where it should be avoided.
> 
> 
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