[gentoo-user] --jobs is ignored for unmerging?

[gentoo-user] --jobs is ignored for unmerging?

[Nikos Chantziaras]

I recently needed to unmerge Netbeans and KDE from a machine. So removed 
the top-level packages of those, and then ran:

   emerge -a --depclean --jobs 20

However, "--jobs" is being ignored. So I'm sitting there, watching 
hundreds of packages being unmerged one by one, taking a long time :-/

Is this normal? Shouldn't the --jobs option result in emerge unmerging 
multiple packages at the same time?

[gentoo-user] Re: --jobs is ignored for unmerging?

[eroen]

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On Fri, 21 Feb 2014 16:14:00 +0200, Nikos Chantziaras
<realnc@gmail.com> wrote:
> I recently needed to unmerge Netbeans and KDE from a machine. So
> removed the top-level packages of those, and then ran:
> 
>    emerge -a --depclean --jobs 20
> 
> However, "--jobs" is being ignored. So I'm sitting there, watching 
> hundreds of packages being unmerged one by one, taking a long time :-/
> 
> Is this normal? Shouldn't the --jobs option result in emerge
> unmerging multiple packages at the same time?
> 

From emerge(1)[1]:
       -j [JOBS], --jobs[=JOBS]
              Specifies  the  number of packages to build
              simultaneously. (...)

In the past, unmerging was almost entirely IO bound, and running
several in parallel would have (at best) no significant speedup. I
suspect the (fairly recent) preserve-libs feature and detection of
unmodified configuration files introduced some cpu-intensive parts,
which might be parallelizeable to some extent if you sacrifice some of
the recoverability of an aborted unmerge.

If you can benchmark low IO utilization during unmerges, I suggest you
open a feature request bug on <bugs.gentoo.org> requesting parallel
unmerge. :-)

In the mean time, you might be able to speed the process up somewhat by
setting FEATURES="-merge-sync" in the environment when you do unmerges.
(see make.conf(5)[2])

1: https://dev.gentoo.org/~zmedico/portage/doc/man/emerge.1.html
2: https://dev.gentoo.org/~zmedico/portage/doc/man/make.conf.5.html

-- 
eroen

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Re: [gentoo-user] --jobs is ignored for unmerging?

[Neil Bothwick]

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On Fri, 21 Feb 2014 16:14:00 +0200, Nikos Chantziaras wrote:

> I recently needed to unmerge Netbeans and KDE from a machine. So
> removed the top-level packages of those, and then ran:
> 
>    emerge -a --depclean --jobs 20
> 
> However, "--jobs" is being ignored. So I'm sitting there, watching 
> hundreds of packages being unmerged one by one, taking a long time :-/

--jobs applies to the compilation phase of emerge. You can see that it is
only ever installing one package at a time, so it is not surprising that
the same applies to uninstalling. It makes sense, at least from the
install perspective, portage checks for file collisions, if two packages
tried to install the same file concurrently, it wouldn't be able to deal
with the collision.


-- 
Neil Bothwick

Accordion: a bagpipe with pleats.

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