From: Dario Faggioli <dfaggioli@suse.com>
To: Juergen Gross <jgross@suse.com>, xen-devel@lists.xenproject.org
Cc: Stefano Stabellini <sstabellini@kernel.org>, Wei Liu <wl@xen.org>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
George Dunlap <George.Dunlap@eu.citrix.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Tim Deegan <tim@xen.org>, Julien Grall <julien.grall@arm.com>,
Jan Beulich <jbeulich@suse.com>,
Ian Jackson <ian.jackson@eu.citrix.com>
Subject: Re: [Xen-devel] [PATCH v3 2/4] xen/sched: remove cpu from pool0 before removing it
Date: Fri, 13 Sep 2019 19:27:20 +0200 [thread overview]
Message-ID: <bdf39183da171d3780318f3c50818906a6a4b487.camel@suse.com> (raw)
In-Reply-To: <20190909093339.7134-3-jgross@suse.com>
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On Mon, 2019-09-09 at 11:33 +0200, Juergen Gross wrote:
> Today a cpu which is removed from the system is taken directly from
> Pool0 to the offline state. This will conflict with the new idle
> scheduler, so remove it from Pool0 first. Additionally accept
> removing
> a free cpu instead of requiring it to be in Pool0.
>
> For the resume failed case we need to call the scheduler code for
> that
> situation after the cpupool handling, so move the scheduler code into
> a function and call it from cpupool_cpu_remove_forced() and remove
> the
> CPU_RESUME_FAILED case from cpu_schedule_callback().
>
> Note that we are calling now schedule_cpu_switch() in stop_machine
> context so we need to switch from spinlock_irq to spinlock_irqsave.
>
So, I was looking at this patch, and while doing that, also trying it
out.
I've done the following:
# echo 0 > /sys/devices/system/xen_cpu/xen_cpu7/online
And CPU 7 went offline, and was listed among the free CPUs:
(XEN) Online Cpus: 0-6
(XEN) Free Cpus: 7
(XEN) Cpupool 0:
(XEN) Cpus: 0-6
(XEN) Scheduler: SMP Credit Scheduler rev2 (credit2)
(XEN) Active queues: 1
(XEN) default-weight = 256
(XEN) Runqueue 0:
(XEN) ncpus = 7
(XEN) cpus = 0-6
(XEN) max_weight = 256
(XEN) pick_bias = 1
(XEN) instload = 1
(XEN) aveload = 3992 (~1%)
(XEN) idlers: 0000006f
(XEN) tickled: 00000000
(XEN) fully idle cores: 0000004f
Then, I did:
# echo 1 > /sys/devices/system/xen_cpu/xen_cpu7/online
And again it appear to have worked, i.e., the CPU is back online and in
Pool-0:
(XEN) Online Cpus: 0-7
(XEN) Cpupool 0:
(XEN) Cpus: 0-7
(XEN) Scheduler: SMP Credit Scheduler rev2 (credit2)
(XEN) Active queues: 1
(XEN) default-weight = 256
(XEN) Runqueue 0:
(XEN) ncpus = 8
(XEN) cpus = 0-7
(XEN) max_weight = 256
(XEN) pick_bias = 1
(XEN) instload = 2
(XEN) aveload = 271474 (~103%)
(XEN) idlers: 000000af
(XEN) tickled: 00000000
(XEN) fully idle cores: 0000008f
Then I did:
# echo 0 > /sys/devices/system/xen_cpu/xen_cpu7/online
And, after that:
# xl cpupool-cpu-remove Pool-0 7
And the system hanged.
I don't have a working serial console on that testbox, unfortunately,
so I can't poke at debug keys, etc.
Is this anything that you've seen or that you can reproduce?
Regards
--
Dario Faggioli, Ph.D
http://about.me/dario.faggioli
Virtualization Software Engineer
SUSE Labs, SUSE https://www.suse.com/
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next prev parent reply other threads:[~2019-09-13 17:27 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-09 9:33 [Xen-devel] [PATCH v3 0/4] xen/sched: use new idle scheduler for free cpus Juergen Gross
2019-09-09 9:33 ` [Xen-devel] [PATCH v3 1/4] xen/sched: populate cpupool0 only after all cpus are up Juergen Gross
2019-09-13 16:54 ` Dario Faggioli
2019-09-09 9:33 ` [Xen-devel] [PATCH v3 2/4] xen/sched: remove cpu from pool0 before removing it Juergen Gross
2019-09-13 17:27 ` Dario Faggioli [this message]
2019-09-14 5:04 ` Juergen Gross
2019-09-09 9:33 ` [Xen-devel] [PATCH v3 3/4] xen/sched: add minimalistic idle scheduler for free cpus Juergen Gross
2019-09-09 9:33 ` [Xen-devel] [PATCH v3 4/4] xen/sched: switch to debugtrace in cpupool handling Juergen Gross
2019-09-12 8:24 ` Dario Faggioli
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