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From: Peter Zijlstra <peterz@infradead.org>
To: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Alexander Duyck <alexanderduyck@fb.com>,
	Alex Williamson <alex.williamson@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Ben Segall <bsegall@google.com>,
	Cornelia Huck <cohuck@redhat.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Herbert Xu <herbert@gondor.apana.org.au>,
	Ingo Molnar <mingo@redhat.com>, Jason Gunthorpe <jgg@nvidia.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Josh Triplett <josh@joshtriplett.org>,
	Michal Hocko <mhocko@suse.com>, Nico Pache <npache@redhat.com>,
	Pasha Tatashin <pasha.tatashin@soleen.com>,
	Steffen Klassert <steffen.klassert@secunet.com>,
	Steve Sistare <steven.sistare@oracle.com>,
	Tejun Heo <tj@kernel.org>, Tim Chen <tim.c.chen@linux.intel.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	linux-mm@kvack.org, kvm@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org
Subject: Re: [RFC 15/16] sched/fair: Account kthread runtime debt for CFS bandwidth
Date: Fri, 14 Jan 2022 10:40:06 +0100	[thread overview]
Message-ID: <YeFE9j4Qynp9sNXS@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <YeFDC0mV3yurUFbl@hirez.programming.kicks-ass.net>

On Fri, Jan 14, 2022 at 10:31:55AM +0100, Peter Zijlstra wrote:

> Also, by virtue of this being a start-stop annotation interface, the
> accrued time might be arbitrarily large and arbitrarily delayed. I'm not
> sure that's sensible.
> 
> For tasks it might be better to mark the task and have the tick DTRT
> instead of later trying to 'migrate' the time.

Which is then very close to simply sticking the task into the right
cgroup for a limited duration.

You could do a special case sched_move_task(), that takes a css argument
instead of using the current task_css. Then for cgroups it looks like
nothing changes, but the scheduler will DTRT and act like it is in the
target cgroup. Then at the end, simply move it back to task_css.

This obviously doesn't work for SoftIRQ accounting, but that is
'special' anyway. Softirq stuff is not otherwise under scheduler
control and has preemption disabled.

  reply	other threads:[~2022-01-14  9:40 UTC|newest]

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-06  0:46 [RFC 00/16] padata, vfio, sched: Multithreaded VFIO page pinning Daniel Jordan
2022-01-06  0:46 ` [RFC 01/16] padata: Remove __init from multithreading functions Daniel Jordan
2022-01-06  0:46 ` [RFC 02/16] padata: Return first error from a job Daniel Jordan
2022-01-06  0:46 ` [RFC 03/16] padata: Add undo support Daniel Jordan
2022-01-06  0:46 ` [RFC 04/16] padata: Detect deadlocks between main and helper threads Daniel Jordan
2022-01-06  0:46 ` [RFC 05/16] vfio/type1: Pass mm to vfio_pin_pages_remote() Daniel Jordan
2022-01-06  0:46 ` [RFC 06/16] vfio/type1: Refactor dma map removal Daniel Jordan
2022-01-06  0:46 ` [RFC 07/16] vfio/type1: Parallelize vfio_pin_map_dma() Daniel Jordan
2022-01-06  0:46 ` [RFC 08/16] vfio/type1: Cache locked_vm to ease mmap_lock contention Daniel Jordan
2022-01-06  0:53   ` Jason Gunthorpe
2022-01-06  1:17     ` Daniel Jordan
2022-01-06 12:34       ` Jason Gunthorpe
2022-01-06 21:05         ` Alex Williamson
2022-01-07  0:19           ` Jason Gunthorpe
2022-01-07  3:06             ` Daniel Jordan
2022-01-07 15:18               ` Jason Gunthorpe
2022-01-07 16:39                 ` Daniel Jordan
2022-01-06  0:46 ` [RFC 09/16] padata: Use kthreads in do_multithreaded Daniel Jordan
2022-01-06  0:46 ` [RFC 10/16] padata: Helpers should respect main thread's CPU affinity Daniel Jordan
2022-01-06  0:46 ` [RFC 11/16] padata: Cap helpers started to online CPUs Daniel Jordan
2022-01-06  0:46 ` [RFC 12/16] sched, padata: Bound max threads with max_cfs_bandwidth_cpus() Daniel Jordan
2022-01-06  6:06   ` kernel test robot
2022-01-06 11:31   ` kernel test robot
2022-01-06  0:46 ` [RFC 13/16] padata: Run helper threads at MAX_NICE Daniel Jordan
2022-01-06  0:46 ` [RFC 14/16] padata: Nice helper threads one by one to prevent starvation Daniel Jordan
2022-01-06  0:46 ` [RFC 15/16] sched/fair: Account kthread runtime debt for CFS bandwidth Daniel Jordan
2022-01-06  6:47   ` kernel test robot
2022-01-06  6:47   ` kernel test robot
2022-01-06  6:47     ` kernel test robot
2022-01-11 11:58   ` Peter Zijlstra
2022-01-11 16:29     ` Daniel Jordan
2022-01-12 20:18       ` Tejun Heo
2022-01-13 21:08         ` Daniel Jordan
2022-01-13 21:11           ` Daniel Jordan
2022-01-14  9:31   ` Peter Zijlstra
2022-01-14  9:40     ` Peter Zijlstra [this message]
2022-01-14 16:38       ` Tejun Heo
2022-01-18 17:40       ` Daniel Jordan
2022-01-14 16:30     ` Tejun Heo
2022-01-18 17:32     ` Daniel Jordan
2022-01-06  0:46 ` [RFC 16/16] sched/fair: Consider kthread debt in cputime Daniel Jordan
2022-01-06  1:13 ` [RFC 00/16] padata, vfio, sched: Multithreaded VFIO page pinning Jason Gunthorpe
2022-01-07  3:03   ` Daniel Jordan
2022-01-07 17:12     ` Jason Gunthorpe
2022-01-10 22:27       ` Daniel Jordan
2022-01-11  0:17         ` Jason Gunthorpe
2022-01-11 16:20           ` Daniel Jordan

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