From: Frederic Weisbecker <frederic@kernel.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
Frederic Weisbecker <frederic@kernel.org>,
Anna-Maria Gleixner <anna-maria@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>
Subject: [RFC PATCH 00/10] timer: Reduce timers softirq (and other optimizations)
Date: Wed, 1 Jul 2020 03:10:20 +0200 [thread overview]
Message-ID: <20200701011030.14324-1-frederic@kernel.org> (raw)
Juri Lelli has reported that threaded IRQs don't go along well with
full dynticks.
The tick never manages to stop due to the following endless loop:
* Timer tick raises timer softirq
* Ksoftirqd wakes up, restarts the tick (2 tasks in the runqueue)
* Timer tick raises timer softirq
* Ksoftirqd wakes up, etc...
The main issue here is that the tick fires the timer tick unconditionally,
whether timers have expired or not. This set is a proposal to lower that.
The 1st patch is actually a bugfix for a theoretical issue that I haven't
observed in practice. But who knows?
Patch 2 is a consolidation.
Patch 3 and 4 are optimizations.
The rest is about timer softirqs.
git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git
timers/softirq
HEAD: d0567dd5546d1f32eca3772a431488f8b0ac26a1
Thanks,
Frederic
---
Frederic Weisbecker (10):
timer: Prevent base->clk from moving backward
timer: Move trigger_dyntick_cpu() to enqueue_timer()
timer: Simplify LVL_START() and calc_index()
timer: Optimize _next_timer_interrupt() level iteration
timers: Always keep track of next expiry
timer: Reuse next expiry cache after nohz exit
timer: Expand clk forward logic beyond nohz
timer: Spare timer softirq until next expiry
timer: Remove must_forward_clk
timer: Lower base clock forwarding threshold
kernel/time/timer.c | 179 +++++++++++++++++++---------------------------------
1 file changed, 64 insertions(+), 115 deletions(-)
next reply other threads:[~2020-07-01 1:10 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-01 1:10 Frederic Weisbecker [this message]
2020-07-01 1:10 ` [RFC PATCH 01/10] timer: Prevent base->clk from moving backward Frederic Weisbecker
2020-07-01 16:35 ` Juri Lelli
2020-07-01 23:20 ` Frederic Weisbecker
2020-07-02 9:59 ` Juri Lelli
2020-07-02 14:04 ` Frederic Weisbecker
2020-07-02 14:32 ` Frederic Weisbecker
2020-07-02 15:57 ` Juri Lelli
2020-07-02 9:48 ` Thomas Gleixner
2020-07-01 1:10 ` [RFC PATCH 02/10] timer: Move trigger_dyntick_cpu() to enqueue_timer() Frederic Weisbecker
2020-07-01 1:10 ` [RFC PATCH 03/10] timer: Simplify LVL_START() and calc_index() Frederic Weisbecker
2020-07-02 11:59 ` Thomas Gleixner
2020-07-02 12:27 ` Frederic Weisbecker
2020-07-01 1:10 ` [RFC PATCH 04/10] timer: Optimize _next_timer_interrupt() level iteration Frederic Weisbecker
2020-07-01 1:10 ` [RFC PATCH 05/10] timers: Always keep track of next expiry Frederic Weisbecker
2020-07-01 1:10 ` [RFC PATCH 06/10] timer: Reuse next expiry cache after nohz exit Frederic Weisbecker
2020-07-01 1:10 ` [RFC PATCH 07/10] timer: Expand clk forward logic beyond nohz Frederic Weisbecker
2020-07-01 1:10 ` [RFC PATCH 08/10] timer: Spare timer softirq until next expiry Frederic Weisbecker
2020-07-01 1:10 ` [RFC PATCH 09/10] timer: Remove must_forward_clk Frederic Weisbecker
2020-07-01 1:10 ` [RFC PATCH 10/10] timer: Lower base clock forwarding threshold Frederic Weisbecker
2020-07-02 13:21 ` Thomas Gleixner
2020-07-02 13:32 ` Frederic Weisbecker
2020-07-02 15:14 ` Thomas Gleixner
2020-07-03 0:12 ` Frederic Weisbecker
2020-07-03 9:13 ` Thomas Gleixner
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