From: Alexander Graf <agraf@suse.de>
To: kernelfans@gmail.com, linuxppc-dev@lists.ozlabs.org,
kvm-ppc@vger.kernel.org
Cc: Paul Mackerras <paulus@samba.org>
Subject: Re: [RFC 00/11]: powerKVM, release the compute power of secondary hwthread on host
Date: Tue, 18 Nov 2014 18:54:40 +0100 [thread overview]
Message-ID: <546B87E0.3070802@suse.de> (raw)
In-Reply-To: <1413487800-7162-1-git-send-email-kernelfans@gmail.com>
On 16.10.14 21:29, kernelfans@gmail.com wrote:
> Nowadays, when running powerKVM(book3s, hv mode), we should make the secondary hwthread
> offline. Which means that if we run misc tsks other than dedicated KVM (e.g mix java and KVM),
> we will lose the compute power of the secondary hwthread on host env.
I'm personally more concerned about IO threads and the likes blocking
CPUs that could do actual work.
But really, IMHO this should just get fixed in hardware. The patch set
looks like quite a good addition of complexity to an already complex
problem - which means it will definitely break :).
Couldn't we just do something as simple as partition the system into SMT
and non-SMT cores? Then the user can just say "keep 2 cores in SMT mode"
and we would refuse to run KVM threads on those.
But then again we would bounce on these threads and increase latency on
entry if we happen to get scheduled there, so it's probably not a win
either.
I really don't have a good answer, except for "POWER8 wasn't designed
for this".
Alex
prev parent reply other threads:[~2014-11-18 17:54 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-16 19:29 [RFC 00/11]: powerKVM, release the compute power of secondary hwthread on host kernelfans
2014-10-16 19:29 ` [RFC 01/11] sched: introduce sys_cpumask in tsk to adapt asymmetric system kernelfans
2014-11-12 9:22 ` Srikar Dronamraju
2014-11-18 5:07 ` Liu ping fan
2014-10-16 19:29 ` [RFC 02/11] powerpc: kvm: ensure vcpu-thread run only on primary hwthread kernelfans
2014-11-12 10:17 ` Srikar Dronamraju
2014-10-16 19:29 ` [RFC 03/11] powerpc: kvm: add interface to control kvm function on a core kernelfans
2014-10-27 4:04 ` Preeti U Murthy
2014-11-18 5:17 ` Liu ping fan
2014-11-12 13:01 ` Srikar Dronamraju
2014-10-16 19:29 ` [RFC 04/11] powerpc: kvm: introduce a kthread on primary thread to anti tickless kernelfans
2014-10-27 4:45 ` Preeti U Murthy
2014-11-18 5:24 ` Liu ping fan
2014-10-16 19:29 ` [RFC 05/11] sched: introduce stop_cpus_async() to schedule special tsk on cpu kernelfans
2014-10-16 19:29 ` [RFC 06/11] powerpc: kvm: introduce online in paca to indicate whether cpu is needed by host kernelfans
2014-10-27 5:32 ` Preeti U Murthy
2014-11-18 5:29 ` Liu ping fan
2014-10-16 19:29 ` [RFC 07/11] powerpc: kvm: the stopper func to cease secondary hwthread kernelfans
2014-10-22 7:12 ` Preeti U Murthy
2014-10-27 6:07 ` Preeti U Murthy
2014-10-16 19:29 ` [RFC 08/11] powerpc: kvm: add a flag in vcore to sync primary with secondry hwthread kernelfans
2014-10-27 6:28 ` Preeti U Murthy
2014-10-16 19:29 ` [RFC 09/11] powerpc: kvm: handle time base on secondary hwthread kernelfans
2014-10-27 6:40 ` Preeti U Murthy
2014-11-18 5:43 ` Liu ping fan
2014-10-16 19:29 ` [RFC 10/11] powerpc: kvm: on_primary_thread() force the secondary threads into NAP mode kernelfans
2014-10-16 19:30 ` [RFC 11/11] powerpc: kvm: Kconfig add an option for enabling secondary hwthread kernelfans
2014-10-27 6:44 ` Preeti U Murthy
2014-11-18 5:47 ` Liu ping fan
2014-11-18 17:54 ` Alexander Graf [this message]
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