* [PATCH] perf/core: Fix account interrupt throttle
@ 2023-01-12 3:38 Yang Jihong
2023-01-28 1:28 ` Yang Jihong
0 siblings, 1 reply; 3+ messages in thread
From: Yang Jihong @ 2023-01-12 3:38 UTC (permalink / raw)
To: peterz, mingo, acme, mark.rutland, alexander.shishkin, jolsa,
namhyung, linux-perf-users, linux-kernel
Cc: yangjihong1
In literal sense of "max_samples_per_tick", if hwc->interrupts ==
max_samples_per_tick, it should not be throttled, therefore, the judgment
condition should be changed to "hwc->interrupts > max_samples_per_tick".
In fact, this may cause the hardlockup to fail, The minimum value of
max_samples_per_tick may be 1, in this case, the return value of
__perf_event_account_interrupt function is 1.
As a result, nmi_watchdog gets throttled, which would stop PMU (Use x86
architecture as an example, see x86_pmu_handle_irq).
Signed-off-by: Yang Jihong <yangjihong1@huawei.com>
---
kernel/events/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index d56328e5080e..ced98e028d86 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -9414,7 +9414,7 @@ __perf_event_account_interrupt(struct perf_event *event, int throttle)
} else {
hwc->interrupts++;
if (unlikely(throttle
- && hwc->interrupts >= max_samples_per_tick)) {
+ && hwc->interrupts > max_samples_per_tick)) {
__this_cpu_inc(perf_throttled_count);
tick_dep_set_cpu(smp_processor_id(), TICK_DEP_BIT_PERF_EVENTS);
hwc->interrupts = MAX_INTERRUPTS;
--
2.30.GIT
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] perf/core: Fix account interrupt throttle
2023-01-12 3:38 [PATCH] perf/core: Fix account interrupt throttle Yang Jihong
@ 2023-01-28 1:28 ` Yang Jihong
2023-02-06 1:28 ` Yang Jihong
0 siblings, 1 reply; 3+ messages in thread
From: Yang Jihong @ 2023-01-28 1:28 UTC (permalink / raw)
To: peterz, mingo, acme, mark.rutland, alexander.shishkin, jolsa,
namhyung, linux-perf-users, linux-kernel
Hello,
PING
Thanks,
Yang
On 2023/1/12 11:38, Yang Jihong wrote:
> In literal sense of "max_samples_per_tick", if hwc->interrupts ==
> max_samples_per_tick, it should not be throttled, therefore, the judgment
> condition should be changed to "hwc->interrupts > max_samples_per_tick".
>
> In fact, this may cause the hardlockup to fail, The minimum value of
> max_samples_per_tick may be 1, in this case, the return value of
> __perf_event_account_interrupt function is 1.
> As a result, nmi_watchdog gets throttled, which would stop PMU (Use x86
> architecture as an example, see x86_pmu_handle_irq).
>
> Signed-off-by: Yang Jihong <yangjihong1@huawei.com>
> ---
> kernel/events/core.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index d56328e5080e..ced98e028d86 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -9414,7 +9414,7 @@ __perf_event_account_interrupt(struct perf_event *event, int throttle)
> } else {
> hwc->interrupts++;
> if (unlikely(throttle
> - && hwc->interrupts >= max_samples_per_tick)) {
> + && hwc->interrupts > max_samples_per_tick)) {
> __this_cpu_inc(perf_throttled_count);
> tick_dep_set_cpu(smp_processor_id(), TICK_DEP_BIT_PERF_EVENTS);
> hwc->interrupts = MAX_INTERRUPTS;
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] perf/core: Fix account interrupt throttle
2023-01-28 1:28 ` Yang Jihong
@ 2023-02-06 1:28 ` Yang Jihong
0 siblings, 0 replies; 3+ messages in thread
From: Yang Jihong @ 2023-02-06 1:28 UTC (permalink / raw)
To: peterz, mingo, acme, mark.rutland, alexander.shishkin, jolsa,
namhyung, linux-perf-users, linux-kernel
Hello,
Ping again, please take time to review, thanks.
Thanks,
Yang
On 2023/1/28 9:28, Yang Jihong wrote:
> Hello,
>
> PING
>
> Thanks,
> Yang
>
> On 2023/1/12 11:38, Yang Jihong wrote:
>> In literal sense of "max_samples_per_tick", if hwc->interrupts ==
>> max_samples_per_tick, it should not be throttled, therefore, the judgment
>> condition should be changed to "hwc->interrupts > max_samples_per_tick".
>>
>> In fact, this may cause the hardlockup to fail, The minimum value of
>> max_samples_per_tick may be 1, in this case, the return value of
>> __perf_event_account_interrupt function is 1.
>> As a result, nmi_watchdog gets throttled, which would stop PMU (Use x86
>> architecture as an example, see x86_pmu_handle_irq).
>>
>> Signed-off-by: Yang Jihong <yangjihong1@huawei.com>
>> ---
>> kernel/events/core.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/kernel/events/core.c b/kernel/events/core.c
>> index d56328e5080e..ced98e028d86 100644
>> --- a/kernel/events/core.c
>> +++ b/kernel/events/core.c
>> @@ -9414,7 +9414,7 @@ __perf_event_account_interrupt(struct perf_event
>> *event, int throttle)
>> } else {
>> hwc->interrupts++;
>> if (unlikely(throttle
>> - && hwc->interrupts >= max_samples_per_tick)) {
>> + && hwc->interrupts > max_samples_per_tick)) {
>> __this_cpu_inc(perf_throttled_count);
>> tick_dep_set_cpu(smp_processor_id(),
>> TICK_DEP_BIT_PERF_EVENTS);
>> hwc->interrupts = MAX_INTERRUPTS;
>>
>
> .
^ permalink raw reply [flat|nested] 3+ messages in thread
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