Re: [patch 10/15] sched/migration: Move calc_load_migrate() into CPU_DYING

Anton Blanchard
2016-07-12T05:02:52Z

Hi Thomas,

> It really does not matter when we fold the load for the outgoing cpu.
> It's almost dead anyway, so there is no harm if we fail to fold the
> few microseconds which are required for going fully away.

We are seeing the load average shoot up when hot unplugging CPUs (+1
for every CPU we offline) on ppc64. This reproduces on bare metal as
well as inside a KVM guest. A bisect points at this commit.

As an example, a completely idle box with 128 CPUS and 112 hot
unplugged:

# uptime
04:35:30 up 1:23, 2 users, load average: 112.43, 122.94, 125.54

Anton