Messages in this thread | | | Date | Thu, 15 Dec 2022 21:36:19 +0800 | Subject | Re: [PATCH RFC 1/8] perf/core: Add *group_leader to perf_event_create_kernel_counter() | From | Like Xu <> |
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On 14/12/2022 11:52 am, Ravi Bangoria wrote: >> diff --git a/kernel/events/core.c b/kernel/events/core.c >> index 7f04f995c975..f671b1a9a691 100644 >> --- a/kernel/events/core.c >> +++ b/kernel/events/core.c >> @@ -12674,12 +12674,14 @@ SYSCALL_DEFINE5(perf_event_open, >> * @attr: attributes of the counter to create >> * @cpu: cpu in which the counter is bound >> * @task: task to profile (NULL for percpu) >> + * @group_leader: event group leader >> * @overflow_handler: callback to trigger when we hit the event >> * @context: context data could be used in overflow_handler callback >> */ >> struct perf_event * >> perf_event_create_kernel_counter(struct perf_event_attr *attr, int cpu, >> struct task_struct *task, >> + struct perf_event *group_leader, >> perf_overflow_handler_t overflow_handler, >> void *context) >> { >> @@ -12694,7 +12696,7 @@ perf_event_create_kernel_counter(struct perf_event_attr *attr, int cpu, >> if (attr->aux_output) >> return ERR_PTR(-EINVAL); >> >> - event = perf_event_alloc(attr, cpu, task, NULL, NULL, >> + event = perf_event_alloc(attr, cpu, task, group_leader, NULL, >> overflow_handler, context, -1); > > Grouping involves lot of complexities. Setting group_leader won't be sufficient. > Please see perf_event_open() syscall code for more detail. > > Thanks, > Ravi
This is the main reason why the RFC tag is added. More detailed professional reviews is encouraged.
AFAI, there does exist a number of code gaps here to support grouped events in the kernel, but there are also opportunities, as there may be other new use cases bringing innovation.
I have to confirm this idea with maintainers first, the alternative is to create yet another special perf_event similar to PMC_IDX_FIXED_VLBR, which schedules perf_metrics MSR for KVM stuff.
PeterZ, any input ?
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