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Scheduling policy switching #861

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wants to merge 1 commit into from
Closed

Scheduling policy switching #861

wants to merge 1 commit into from

Commits on Aug 1, 2022

  1. Scheduling policy switching 

    Adds ability to control the scheduler policy that is used for emerge and
all child processes. Mainly to interface the ability to switch to
SCHED_IDLE as the solution to keep interactive tasks unaffected by
building process happening in the background.

On a test sample N=1 with AMD Ryzen 5950x and 64 GB of ram building
sys-devel/gcc with lto enabled significantly reduces responsiveness of
the system, even with CONFIG_SCHED_AUTOGROUP and PREEMPT enabled. Using
a web browser result in visible lags, video playback in web browser,
when using CPU decoding, also suffers greatly.

Switching Portage to SCHED_IDLE (PORTAGE_SCHEDULING_POLICY="idle")
results in no visible slowdowns and responsiveness is as if nothing in
the background was happening.

This is especially worthy feature when running on powerful CPUs, where
users often opt in to build not only with parallel build jobs, but also
with multiple packages at once. Anyone running with PORTAGE_NICENESS="19" will
undoubtedly want to use this feature to force SCHED_IDLE policy.

Signed-off-by: KARBOWSKI Piotr <slashbeast@gentoo.org>
    KARBOWSKI Piotr committed Aug 1, 2022
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