linux-kernel - Re: [PATCH 3/3] sched: Implement interface for cgroup unified hierarchy

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Date:	Wed, 19 Aug 2015 08:39:43 +0900
From:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Tejun Heo <tj@...nel.org>, Paul Turner <pjt@...gle.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>, lizefan@...wei.com,
	cgroups <cgroups@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	kernel-team <kernel-team@...com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 3/3] sched: Implement interface for cgroup unified
 hierarchy

On 2015/08/19 5:31, Tejun Heo wrote:
> Hello, Paul.
>
> On Mon, Aug 17, 2015 at 09:03:30PM -0700, Paul Turner wrote:
>>> 2) Control within an address-space.  For subsystems with fungible resources,
>>> e.g. CPU, it can be useful for an address space to partition its own
>>> threads.  Losing the capability to do this against the CPU controller would
>>> be a large set-back for instance.  Occasionally, it is useful to share these
>>> groupings between address spaces when processes are cooperative, but this is
>>> less of a requirement.
>>>
>>> This is important to us.
>
> Sure, let's build a proper interface for that.  Do you actually need
> sub-hierarchy inside a process?  Can you describe your use case in
> detail and why having hierarchical CPU cycle distribution is essential
> for your use case?

An actual per-thread use case in our customers is qemu-kvm + cpuset.
customers pin each vcpus and qemu-kvm's worker threads to cpus.
For example, pinning 4 vcpus to cpu 2-6 and pinning qemu main thread and
others(vhost) to cpu 0-1.

This is an actual kvm tuning on our customers for performance guarantee.

In another case, cpu cgroup's throttling feature is used per vcpu for vm cpu sizing.

Thanks,
-Kame

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