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

From	Anton Blanchard <anton@samba.org>
Newsgroups	linux.kernel
Subject	Re: [patch 10/15] sched/migration: Move calc_load_migrate() into CPU_DYING
Date	2016-07-12 07:10 +0200
Message-ID	<rTY7f-ra-1@gated-at.bofh.it> (permalink)
References	<rb7zI-6OQ-3@gated-at.bofh.it> <rb7zI-6OQ-13@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

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

Back to linux.kernel | Previous | Next — Next in thread | Find similar | Unroll thread

Thread

Re: [patch 10/15] sched/migration: Move calc_load_migrate() into  CPU_DYING Anton Blanchard <anton@samba.org> - 2016-07-12 07:10 +0200
  Re: [patch 10/15] sched/migration: Move calc_load_migrate() into  CPU_DYING Thomas Gleixner <tglx@linutronix.de> - 2016-07-12 18:40 +0200
    Re: [patch 10/15] sched/migration: Move calc_load_migrate() into  CPU_DYING Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com> - 2016-07-12 21:00 +0200
    Re: [patch 10/15] sched/migration: Move calc_load_migrate() into  CPU_DYING Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com> - 2016-07-12 22:10 +0200
    Re: [patch 10/15] sched/migration: Move calc_load_migrate() into  CPU_DYING Peter Zijlstra <peterz@infradead.org> - 2016-07-13 10:00 +0200
    [tip:sched/urgent] sched/core: Correct off by one bug in load  migration calculation tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-07-13 15:50 +0200

csiph-web