From: Chris Metcalf <cmetcalf@ezchip.com>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Preeti U Murthy <preeti@linux.vnet.ibm.com>,
Christoph Lameter <cl@linux.com>, Ingo Molnar <mingo@kernel.org>,
Viresh Kumar <viresh.kumar@linaro.org>,
Rik van Riel <riel@redhat.com>
Subject: Re: [PATCH 08/10] posix-cpu-timers: Migrate to use new tick dependency mask model
Date: Mon, 3 Aug 2015 11:59:07 -0400 [thread overview]
Message-ID: <55BF8FCB.6060409@ezchip.com> (raw)
In-Reply-To: <20150731144954.GB27875@lerouge>
On 07/31/2015 10:49 AM, Frederic Weisbecker wrote:
> Instead of doing a per signal dependency, I'm going to use a per task
> one. Which means that if a per-process timer is enqueued, every thread
> of that process will have the tick dependency. But if the timer is
> enqueued to a single thread, only the thread is concerned.
>
> We'll see if offloading becomes really needed. It's not quite free because
> the housekeepers will have to poll on all nohz CPUs at a Hz frequency.
Seems reasonable for now!
Why would we need the Hz frequency polling, though? I would
think it should be possible to just arrange it such that the timer
for posix cpu timers would just always be placed either on the core
that requested it, or if that core is nohz_full, on a housekeeping
core. Then it would eventually fire from the housekeeping core,
and the logic could be such that (for a process-wide timer) it
would preferentially interrupt threads from that process that
were running on the housekeeping cores. No polling.
--
Chris Metcalf, EZChip Semiconductor
http://www.ezchip.com
next prev parent reply other threads:[~2015-08-03 15:59 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-23 16:42 [PATCH 00/10] nohz: Tick dependency mask v2 Frederic Weisbecker
2015-07-23 16:42 ` [PATCH 01/10] nohz: Remove idle task special case Frederic Weisbecker
2015-07-23 16:42 ` [PATCH 02/10] nohz: Restart nohz full tick from irq exit Frederic Weisbecker
2015-07-23 16:42 ` [PATCH 03/10] nohz: Move tick_nohz_restart_sched_tick() above its users Frederic Weisbecker
2015-07-23 16:42 ` [PATCH 04/10] nohz: Remove useless argument on tick_nohz_task_switch() Frederic Weisbecker
2015-08-03 12:39 ` Peter Zijlstra
2015-08-03 12:49 ` Frederic Weisbecker
2015-08-03 13:04 ` Peter Zijlstra
2015-07-23 16:42 ` [PATCH 05/10] nohz: New tick dependency mask Frederic Weisbecker
2015-07-24 16:55 ` Chris Metcalf
2015-07-24 17:16 ` Frederic Weisbecker
2015-07-24 17:43 ` Chris Metcalf
2015-08-03 12:48 ` Peter Zijlstra
2015-08-03 12:43 ` Peter Zijlstra
2015-08-03 13:05 ` Frederic Weisbecker
2015-08-03 13:24 ` Peter Zijlstra
2015-08-03 13:49 ` Frederic Weisbecker
2015-08-03 12:57 ` Peter Zijlstra
2015-08-03 13:09 ` Frederic Weisbecker
2015-08-03 13:29 ` Peter Zijlstra
2015-08-03 13:55 ` Frederic Weisbecker
2015-08-03 14:11 ` Peter Zijlstra
2015-07-23 16:42 ` [PATCH 06/10] perf: Migrate perf to use new tick dependency mask model Frederic Weisbecker
2015-07-23 16:42 ` [PATCH 07/10] sched: Migrate sched " Frederic Weisbecker
2015-07-23 16:55 ` Frederic Weisbecker
2015-07-24 16:56 ` Chris Metcalf
2015-07-29 13:01 ` Frederic Weisbecker
2015-08-03 14:00 ` Peter Zijlstra
2015-08-03 14:50 ` Frederic Weisbecker
2015-08-03 17:09 ` Peter Zijlstra
2015-08-03 17:30 ` Frederic Weisbecker
2015-08-04 7:41 ` Peter Zijlstra
2015-08-10 14:02 ` Juri Lelli
2015-08-10 14:16 ` Frederic Weisbecker
2015-08-10 14:28 ` Peter Zijlstra
2015-08-10 15:11 ` Peter Zijlstra
2015-08-10 15:29 ` Frederic Weisbecker
2015-08-10 15:43 ` Juri Lelli
2015-08-10 16:41 ` Peter Zijlstra
2015-08-10 15:33 ` Christoph Lameter
2015-07-23 16:42 ` [PATCH 08/10] posix-cpu-timers: Migrate " Frederic Weisbecker
2015-07-24 16:57 ` Chris Metcalf
2015-07-29 13:23 ` Frederic Weisbecker
2015-07-29 17:24 ` Chris Metcalf
2015-07-30 0:44 ` Frederic Weisbecker
2015-07-30 14:31 ` Luiz Capitulino
2015-07-30 14:46 ` Frederic Weisbecker
2015-07-30 19:35 ` Chris Metcalf
2015-07-30 19:45 ` Frederic Weisbecker
2015-07-30 19:52 ` Chris Metcalf
2015-07-31 14:49 ` Frederic Weisbecker
2015-08-03 15:59 ` Chris Metcalf [this message]
2015-08-03 18:01 ` Frederic Weisbecker
2015-08-03 17:12 ` Peter Zijlstra
2015-08-03 17:39 ` Frederic Weisbecker
2015-08-03 19:07 ` Peter Zijlstra
2015-08-06 17:13 ` Chris Metcalf
2015-07-23 16:42 ` [PATCH 09/10] sched-clock: " Frederic Weisbecker
2015-07-23 16:42 ` [PATCH 10/10] nohz: Remove task switch obsolete tick dependency check Frederic Weisbecker
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