Messages in this thread Patch in this message | | | Date | Fri, 10 Feb 2017 16:47:58 -0500 | From | Steven Rostedt <> | Subject | Re: [PATCH 1/2] sched/deadline: Replenishment timer should fire in the next period |
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On Fri, 10 Feb 2017 20:48:10 +0100 Daniel Bristot de Oliveira <bristot@redhat.com> wrote:
> Currently, the replenishment timer is set to fire at the deadline > of a task. Although that works for implicit deadline tasks because the > deadline is equals to the begin of the next period, that is not correct > for constrained deadline tasks (deadline < period). > > For instance: > > f.c: > --------------- %< --------------- > int main (void) > { > for(;;); > } > --------------- >% --------------- > > # gcc -o f f.c > > # trace-cmd record -e sched:sched_switch \ > -e syscalls:sys_exit_sched_setattr \ > chrt -d --sched-runtime 490000000 \ > --sched-deadline 500000000 \ > --sched-period 1000000000 0 ./f > > # trace-cmd report | grep "{pid of ./f}"
# trace-cmd report -F '.*:common_pid == 11295'
does the same ;-)
Or better yet, add "-F" (just -F, no extra paremeter. In report, -F means "filter", in record -F means "follow"), and that will only record the task that is created.
Also, it may be nice to use --ts-diff option to see results. I ran this with my own spinning program, and here's the output:
# trace-cmd report --ts-diff [...] userspin-1540 [003] 298.725084: (+822) sys_exit_sched_setattr: 0x0 userspin-1540 [003] 299.218199: (+493115) sched_switch: userspin:1540 [4294967295] R ==> rcuc/3:38 [98] <idle>-0 [003] 299.225111: (+6912) sched_switch: swapper/3:0 [120] R ==> userspin:1540 [4294967295] userspin-1540 [003] 299.718192: (+493081) sched_switch: userspin:1540 [4294967295] R ==> ktimersoftd/3:39 [98] <idle>-0 [003] 300.225125: (+506933) sched_switch: swapper/3:0 [120] R ==> userspin:1540 [4294967295] userspin-1540 [003] 300.717185: (+492060) sched_switch: userspin:1540 [4294967295] R ==> rcuc/3:38 [98] <idle>-0 [003] 301.225116: (+507931) sched_switch: swapper/3:0 [120] R ==> userspin:1540 [4294967295] userspin-1540 [003] 301.718177: (+493061) sched_switch: userspin:1540 [4294967295] R ==> rcuc/3:38 [98] <idle>-0 [003] 302.225120: (+506943) sched_switch: swapper/3:0 [120] R ==> userspin:1540 [4294967295]
> > After setting parameters, the task is replenished and continue running > until being throttled. > f-11295 [003] 13322.113776: sys_exit_sched_setattr: 0x0 > > The task is throttled after running 492318 ms, as expected. > f-11295 [003] 13322.606094: sched_switch: f:11295 [-1] R ==> \ > watchdog/3:32 [0] > > But then, the task is replenished 500719 ms after the first > replenishment: > <idle>-0 [003] 13322.614495: sched_switch: swapper/3:0 [120] R \ > ==> f:11295 [-1] > > Running for 490277 ms: > f-11295 [003] 13323.104772: sched_switch: f:11295 [-1] R ==> \ > swapper/3:0 [120] > > Hence, in the first period, the task runs 2 * runtime, and that is a bug. > > During the first replenishment, the next deadline is set one period away. > So the runtime/period starts to be respected. However, as the second > replenishment took place in the wrong instant, the next replenishment > will also be held in a wrong instant of time. Rather than occurring in > the nth period away from the first activation, it is taking place > in the (nth period - relative deadline).
OK, after you patch, I get this:
userspin-1581 [003] 103.450129: (+716) sys_exit_sched_setattr: 0x0 userspin-1581 [003] 103.943957: (+493828) sched_switch: userspin:1581 [4294967295] R ==> rcuc/3:38 [98] <idle>-0 [003] 104.450172: (+506215) sched_switch: swapper/3:0 [120] R ==> userspin:1581 [4294967295] userspin-1581 [003] 104.942349: (+492177) sched_switch: userspin:1581 [4294967295] R ==> watchdog/3:36 [0] <idle>-0 [003] 105.450164: (+507815) sched_switch: swapper/3:0 [120] R ==> userspin:1581 [4294967295] userspin-1581 [003] 105.942354: (+492190) sched_switch: userspin:1581 [4294967295] R ==> ktimersoftd/3:39 [98] <idle>-0 [003] 106.450159: (+507805) sched_switch: swapper/3:0 [120] R ==> userspin:1581 [4294967295] userspin-1581 [003] 106.942366: (+492207) sched_switch: userspin:1581 [4294967295] R ==> ktimersoftd/3:39 [98] <idle>-0 [003] 107.450164: (+507798) sched_switch: swapper/3:0 [120] R ==> userspin:1581 [4294967295]
Looks promising. But unrelated, I noticed this with and without your patch:
userspin-1567 [002] 81.455345: (+1196) sys_exit_sched_setattr: 0x0 userspin-1567 [002] 81.457599: (+2254) sched_switch: chrt:1567 [4294967295] D ==> rcuc/2:29 [98] <idle>-0 [002] 81.466030: (+8431) sched_switch: swapper/2:0 [120] R ==> chrt:1567 [4294967295] userspin-1567 [002] 81.466123: (+93) sched_switch: chrt:1567 [4294967295] D ==> rcuc/2:29 [98] <idle>-0 [002] 81.471862: (+5739) sched_switch: swapper/2:0 [120] R ==> chrt:1567 [4294967295] userspin-1567 [002] 81.471959: (+97) sched_switch: chrt:1567 [4294967295] D ==> swapper/2:0 [120] <idle>-0 [002] 81.478285: (+6326) sched_switch: swapper/2:0 [120] R ==> chrt:1567 [4294967295] userspin-1567 [002] 81.478369: (+84) sched_switch: chrt:1567 [4294967295] D ==> swapper/2:0 [120] <idle>-0 [002] 81.486664: (+8295) sched_switch: swapper/2:0 [120] R ==> chrt:1567 [4294967295] userspin-1567 [002] 81.487291: (+627) sched_switch: chrt:1567 [4294967295] D|W ==> swapper/2:0 [120] <idle>-0 [002] 81.494884: (+7593) sched_switch: swapper/2:0 [120] R ==> chrt:1567 [4294967295] userspin-1567 [002] 81.988095: (+493211) sched_switch: userspin:1567 [4294967295] R ==> rcuc/2:29 [98] <idle>-0 [002] 82.496009: (+507914) sched_switch: swapper/2:0 [120] R ==> userspin:1567 [4294967295] userspin-1567 [002] 82.988158: (+492149) sched_switch: userspin:1567 [4294967295] R ==> rcuc/2:29 [98] <idle>-0 [002] 83.494897: (+506739) sched_switch: swapper/2:0 [120] R ==> userspin:1567 [4294967295] userspin-1567 [002] 83.986181: (+491284) sched_switch: userspin:1567 [4294967295] R ==> rcuc/2:29 [98] <idle>-0 [002] 84.494895: (+508714) sched_switch: swapper/2:0 [120] R ==> userspin:1567 [4294967295]
A bit of choppiness to get started. I'll have to look more into this.
I'll take a look at this patch deeper to try to understand everything before applying a reviewed-by.
-- Steve
> > Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com> > Cc: Ingo Molnar <mingo@redhat.com> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Juri Lelli <juri.lelli@arm.com> > Cc: Tommaso Cucinotta <tommaso.cucinotta@sssup.it> > Cc: Luca Abeni <luca.abeni@santannapisa.it> > Cc: Steven Rostedt <rostedt@goodmis.org> > Cc: linux-kernel@vger.kernel.org > > --- > kernel/sched/deadline.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c > index 70ef2b1..3c94d85 100644 > --- a/kernel/sched/deadline.c > +++ b/kernel/sched/deadline.c > @@ -505,10 +505,15 @@ static void update_dl_entity(struct sched_dl_entity *dl_se, > } > } > > +static inline u64 dl_next_period(struct sched_dl_entity *dl_se) > +{ > + return dl_se->deadline - dl_se->dl_deadline + dl_se->dl_period; > +} > + > /* > * If the entity depleted all its runtime, and if we want it to sleep > * while waiting for some new execution time to become available, we > - * set the bandwidth enforcement timer to the replenishment instant > + * set the bandwidth replenishment timer to the replenishment instant > * and try to activate it. > * > * Notice that it is important for the caller to know if the timer > @@ -530,7 +535,7 @@ static int start_dl_timer(struct task_struct *p) > * that it is actually coming from rq->clock and not from > * hrtimer's time base reading. > */ > - act = ns_to_ktime(dl_se->deadline); > + act = ns_to_ktime(dl_next_period(dl_se)); > now = hrtimer_cb_get_time(timer); > delta = ktime_to_ns(now) - rq_clock(rq); > act = ktime_add_ns(act, delta);
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