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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>,
	Daniel Drake <drake@endlessm.com>,
	Vinayak Menon <vinmenon@codeaurora.org>,
	Christopher Lameter <cl@linux.com>,
	Peter Enderborg <peter.enderborg@sony.com>,
	Shakeel Butt <shakeelb@google.com>,
	Mike Galbraith <efault@gmx.de>,
	linux-mm@kvack.org, cgroups@vger.kernel.org,
	linux-kernel@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH 8/9] psi: pressure stall information for CPU, memory, and IO
Date: Fri, 7 Sep 2018 16:58:58 +0200	[thread overview]
Message-ID: <20180907145858.GK24106@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20180907144422.GA11088@cmpxchg.org>

On Fri, Sep 07, 2018 at 10:44:22AM -0400, Johannes Weiner wrote:

> > This does the whole seqcount thing 6x, which is a bit of a waste.
> 
> [...]
> 
> > It's a bit cumbersome, but that's because of C.
> 
> I was actually debating exactly this with Suren before, but since this
> is a super cold path I went with readability. I was also thinking that
> restarts could happen quite regularly under heavy scheduler load, and
> so keeping the individual retry sections small could be helpful - but
> I didn't instrument this in any way.

I was hoping going over the whole thing once would reduce the time we
need to keep that line in shared mode and reduce traffic. And yes, this
path is cold, but I was thinking about reducing the interference on the
remote CPU.

Alternatively, we memcpy the whole line under the seqlock and then do
everything later.

Also, this only has a single cpu_clock() invocation.

  reply	other threads:[~2018-09-07 14:59 UTC|newest]

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-28 17:22 [PATCH 0/9] psi: pressure stall information for CPU, memory, and IO v4 Johannes Weiner
2018-08-28 17:22 ` [PATCH 1/9] mm: workingset: don't drop refault information prematurely Johannes Weiner
2018-08-28 17:22 ` [PATCH 2/9] mm: workingset: tell cache transitions from workingset thrashing Johannes Weiner
2018-08-28 17:22 ` [PATCH 3/9] delayacct: track delays from thrashing cache pages Johannes Weiner
2018-08-28 17:22 ` [PATCH 4/9] sched: loadavg: consolidate LOAD_INT, LOAD_FRAC, CALC_LOAD Johannes Weiner
2018-09-12 23:28   ` Andrew Morton
2018-09-13  1:49     ` Johannes Weiner
2018-08-28 17:22 ` [PATCH 5/9] sched: loadavg: make calc_load_n() public Johannes Weiner
2018-08-28 17:22 ` [PATCH 6/9] sched: sched.h: make rq locking and clock functions available in stats.h Johannes Weiner
2018-08-28 17:22 ` [PATCH 7/9] sched: introduce this_rq_lock_irq() Johannes Weiner
2018-08-28 17:22 ` [PATCH 8/9] psi: pressure stall information for CPU, memory, and IO Johannes Weiner
2018-08-28 20:11   ` Randy Dunlap
2018-08-28 20:56     ` Johannes Weiner
2018-08-28 21:30       ` Randy Dunlap
2018-09-07 10:16   ` Peter Zijlstra
2018-09-07 10:21     ` Peter Zijlstra
2018-09-07 14:44     ` Johannes Weiner
2018-09-07 14:58       ` Peter Zijlstra [this message]
2018-09-07 17:50         ` Johannes Weiner
2018-09-07 10:24   ` Peter Zijlstra
2018-09-07 14:54     ` Johannes Weiner
2018-08-28 17:22 ` [PATCH 9/9] psi: cgroup support Johannes Weiner
2018-09-05 21:43 ` [PATCH 0/9] psi: pressure stall information for CPU, memory, and IO v4 Johannes Weiner
2018-09-07  7:36   ` Daniel Drake
2018-09-07  7:46   ` Peter Zijlstra
2018-09-07 11:04   ` Peter Zijlstra
2018-09-07 15:09     ` Johannes Weiner
2018-09-07 15:58       ` Suren Baghdasaryan
2018-09-17  5:22         ` Daniel Drake
2018-09-18 15:53           ` Suren Baghdasaryan
2018-09-25 22:05             ` Suren Baghdasaryan
2018-09-17 13:29         ` peter enderborg
2018-09-17 13:29           ` peter enderborg
2018-09-17 13:40           ` Peter Zijlstra
2018-09-18 16:03           ` Suren Baghdasaryan
2018-10-19  2:07 ` Andrew Morton
2018-10-23 17:29   ` Johannes Weiner
2018-10-23 17:41     ` Peter Zijlstra
  -- strict thread matches above, loose matches on Subject: below --
2018-08-01 15:19 [PATCH 0/9] psi: pressure stall information for CPU, memory, and IO v3 Johannes Weiner
2018-08-01 15:19 ` [PATCH 8/9] psi: pressure stall information for CPU, memory, and IO Johannes Weiner
2018-08-03 16:56   ` Peter Zijlstra
2018-08-06 15:05     ` Johannes Weiner
2018-08-06 15:25       ` Peter Zijlstra
2018-08-06 15:40         ` Johannes Weiner
2018-08-06 15:19     ` Johannes Weiner
2018-08-06 16:03       ` Peter Zijlstra
2018-08-21 19:44     ` Johannes Weiner
2018-08-22  9:16       ` Peter Zijlstra
2018-08-03 17:07   ` Peter Zijlstra
2018-08-06 15:23     ` Johannes Weiner
2018-08-03 17:15   ` Peter Zijlstra
2018-08-03 17:21   ` Peter Zijlstra
2018-08-21 20:11     ` Johannes Weiner
2018-08-22  9:10       ` Peter Zijlstra
2018-08-22 17:28         ` Johannes Weiner
2018-08-01 15:12 Johannes Weiner
2018-08-01 15:13 ` [PATCH 8/9] psi: pressure stall information for CPU, memory, and IO Johannes Weiner

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