diff options
| author | Peng Liu <iwtbavbm@gmail.com> | 2020-10-08 23:49:42 +0800 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2020-10-29 11:00:29 +0100 |
| commit | a57415f5d1e43c3a5c5d412cd85e2792d7ed9b11 (patch) | |
| tree | 3ba2bc5098567e8ac8d0facf4640b189fa6f6b4c /kernel/sched/deadline.c | |
| parent | 26762423a2664692de2bcccc9de684a5ac105e23 (diff) | |
sched/deadline: Fix sched_dl_global_validate()
When change sched_rt_{runtime, period}_us, we validate that the new
settings should at least accommodate the currently allocated -dl
bandwidth:
sched_rt_handler()
--> sched_dl_bandwidth_validate()
{
new_bw = global_rt_runtime()/global_rt_period();
for_each_possible_cpu(cpu) {
dl_b = dl_bw_of(cpu);
if (new_bw < dl_b->total_bw) <-------
ret = -EBUSY;
}
}
But under CONFIG_SMP, dl_bw is per root domain , but not per CPU,
dl_b->total_bw is the allocated bandwidth of the whole root domain.
Instead, we should compare dl_b->total_bw against "cpus*new_bw",
where 'cpus' is the number of CPUs of the root domain.
Also, below annotation(in kernel/sched/sched.h) implied implementation
only appeared in SCHED_DEADLINE v2[1], then deadline scheduler kept
evolving till got merged(v9), but the annotation remains unchanged,
meaningless and misleading, update it.
* With respect to SMP, the bandwidth is given on a per-CPU basis,
* meaning that:
* - dl_bw (< 100%) is the bandwidth of the system (group) on each CPU;
* - dl_total_bw array contains, in the i-eth element, the currently
* allocated bandwidth on the i-eth CPU.
[1]: https://lore.kernel.org/lkml/1267385230.13676.101.camel@Palantir/
Fixes: 332ac17ef5bf ("sched/deadline: Add bandwidth management for SCHED_DEADLINE tasks")
Signed-off-by: Peng Liu <iwtbavbm@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Acked-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lkml.kernel.org/r/db6bbda316048cda7a1bbc9571defde193a8d67e.1602171061.git.iwtbavbm@gmail.com
Diffstat (limited to 'kernel/sched/deadline.c')
| -rw-r--r-- | kernel/sched/deadline.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 98d96d40e202..0f75e95ae024 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -2561,7 +2561,7 @@ int sched_dl_global_validate(void) u64 new_bw = to_ratio(period, runtime); u64 gen = ++dl_generation; struct dl_bw *dl_b; - int cpu, ret = 0; + int cpu, cpus, ret = 0; unsigned long flags; /* @@ -2576,9 +2576,10 @@ int sched_dl_global_validate(void) goto next; dl_b = dl_bw_of(cpu); + cpus = dl_bw_cpus(cpu); raw_spin_lock_irqsave(&dl_b->lock, flags); - if (new_bw < dl_b->total_bw) + if (new_bw * cpus < dl_b->total_bw) ret = -EBUSY; raw_spin_unlock_irqrestore(&dl_b->lock, flags); |