From: Peter Zijlstra <peterz@infradead.org>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Ingo Molnar <mingo@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Tejun Heo <tj@kernel.org>, Suren Baghdasaryan <surenb@google.com>,
Vinayak Menon <vinmenon@codeaurora.org>,
Christopher Lameter <cl@linux.com>,
Mike Galbraith <efault@gmx.de>,
Shakeel Butt <shakeelb@google.com>,
linux-mm@kvack.org, cgroups@vger.kernel.org,
linux-kernel@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH 08/10] psi: pressure stall information for CPU, memory, and IO
Date: Sat, 14 Jul 2018 10:48:01 +0200 [thread overview]
Message-ID: <20180714084801.GB4920@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20180713161756.GA21168@cmpxchg.org>
Hi Johannes,
A few quick comments on first reading; I'll do a second and more
thorough reading on Monday.
On Fri, Jul 13, 2018 at 12:17:56PM -0400, Johannes Weiner wrote:
> First off, what I want to do can indeed be done without a strong link
> of a sleeping task to a CPU. We don't rely on it, and it's something I
> only figured out in v2. The important thing is not, as I previously
> thought, that CPUs are tracked independently from each other, but that
> we use potential execution threads as the baseline for potential that
> could be wasted by resource delays. Tracking CPUs independently just
> happens to do that implicitly, but it's not a requirement.
I don't follow, but I don't think I agree.
Consider the case of 2 CPUs and 2 blocked tasks. If they both blocked on
the same CPU, then only that CPU has lost potential. Whereas the only
thing that matters is the number of blocked tasks and the number of idle
CPUs.
Those two tasks can fill the two idle CPUs. Tracking per CPU just
utterly confuses the matter.
next prev parent reply other threads:[~2018-07-14 8:48 UTC|newest]
Thread overview: 83+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-12 17:29 [PATCH 0/10] psi: pressure stall information for CPU, memory, and IO v2 Johannes Weiner
2018-07-12 17:29 ` [PATCH 01/10] mm: workingset: don't drop refault information prematurely Johannes Weiner
2018-07-12 17:29 ` [PATCH 02/10] mm: workingset: tell cache transitions from workingset thrashing Johannes Weiner
2018-07-23 13:36 ` Arnd Bergmann
2018-07-23 15:23 ` Johannes Weiner
2018-07-23 15:35 ` Arnd Bergmann
2018-07-23 16:27 ` Johannes Weiner
2018-07-24 15:04 ` Will Deacon
2018-07-25 16:06 ` Will Deacon
2018-07-12 17:29 ` [PATCH 03/10] delayacct: track delays from thrashing cache pages Johannes Weiner
2018-07-12 17:29 ` [PATCH 04/10] sched: loadavg: consolidate LOAD_INT, LOAD_FRAC, CALC_LOAD Johannes Weiner
2018-07-12 17:29 ` [PATCH 05/10] sched: loadavg: make calc_load_n() public Johannes Weiner
2018-07-12 17:29 ` [PATCH 06/10] sched: sched.h: make rq locking and clock functions available in stats.h Johannes Weiner
2018-07-12 17:29 ` [PATCH 07/10] sched: introduce this_rq_lock_irq() Johannes Weiner
2018-07-12 17:29 ` [PATCH 08/10] psi: pressure stall information for CPU, memory, and IO Johannes Weiner
2018-07-13 9:21 ` Peter Zijlstra
2018-07-13 16:17 ` Johannes Weiner
2018-07-14 8:48 ` Peter Zijlstra [this message]
2018-07-14 9:02 ` Peter Zijlstra
2018-07-17 10:03 ` Peter Zijlstra
2018-07-18 21:56 ` Johannes Weiner
2018-07-17 14:16 ` Peter Zijlstra
2018-07-18 22:00 ` Johannes Weiner
2018-07-17 14:21 ` Peter Zijlstra
2018-07-18 22:03 ` Johannes Weiner
2018-07-17 15:01 ` Peter Zijlstra
2018-07-18 22:06 ` Johannes Weiner
2018-07-20 14:13 ` Johannes Weiner
2018-07-17 15:17 ` Peter Zijlstra
2018-07-18 22:11 ` Johannes Weiner
2018-07-17 15:32 ` Peter Zijlstra
2018-07-18 12:03 ` Peter Zijlstra
2018-07-18 12:22 ` Peter Zijlstra
2018-07-18 22:36 ` Johannes Weiner
2018-07-19 13:58 ` Peter Zijlstra
2018-07-19 9:26 ` Peter Zijlstra
2018-07-19 12:50 ` Johannes Weiner
2018-07-19 13:18 ` Peter Zijlstra
2018-07-19 15:08 ` Linus Torvalds
2018-07-19 17:54 ` Johannes Weiner
2018-07-19 18:47 ` Johannes Weiner
2018-07-19 20:31 ` Peter Zijlstra
2018-07-24 16:01 ` Johannes Weiner
2018-07-18 12:46 ` Peter Zijlstra
2018-07-18 13:56 ` Johannes Weiner
2018-07-18 16:31 ` Peter Zijlstra
2018-07-18 16:46 ` Johannes Weiner
2018-07-20 20:35 ` Peter Zijlstra
2018-07-12 17:29 ` [PATCH 09/10] psi: cgroup support Johannes Weiner
2018-07-12 20:08 ` Tejun Heo
2018-07-17 15:40 ` Peter Zijlstra
2018-07-24 15:54 ` Johannes Weiner
2018-07-12 17:29 ` [RFC PATCH 10/10] psi: aggregate ongoing stall events when somebody reads pressure Johannes Weiner
2018-07-12 23:45 ` Andrew Morton
2018-07-13 22:17 ` Johannes Weiner
2018-07-13 22:13 ` Suren Baghdasaryan
2018-07-13 22:49 ` Johannes Weiner
2018-07-13 23:34 ` Suren Baghdasaryan
2018-07-17 15:13 ` Peter Zijlstra
2018-07-12 17:37 ` [PATCH 0/10] psi: pressure stall information for CPU, memory, and IO v2 Linus Torvalds
2018-07-12 23:44 ` Andrew Morton
2018-07-13 22:14 ` Johannes Weiner
2018-07-16 15:57 ` Daniel Drake
2018-07-17 11:25 ` Michal Hocko
2018-07-17 12:13 ` Daniel Drake
2018-07-17 12:23 ` Michal Hocko
2018-07-25 22:57 ` Daniel Drake
2018-07-18 22:21 ` Johannes Weiner
2018-07-19 11:29 ` peter enderborg
2018-07-19 12:18 ` Johannes Weiner
2018-07-23 21:14 ` Balbir Singh
2018-07-24 15:15 ` Johannes Weiner
2018-07-26 1:07 ` Singh, Balbir
2018-07-26 20:07 ` Johannes Weiner
2018-07-27 23:40 ` Suren Baghdasaryan
2018-07-27 22:01 ` Pavel Machek
2018-07-30 15:40 ` Johannes Weiner
2018-07-30 17:39 ` Pavel Machek
2018-07-30 17:51 ` Tejun Heo
2018-07-30 17:54 ` Randy Dunlap
2018-07-30 18:05 ` Tejun Heo
2018-07-30 17:59 ` Pavel Machek
2018-07-30 18:07 ` Tejun Heo
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