> On Jun 18, 2020, at 2:09 AM, Athira Rajeev <atraj...@linux.vnet.ibm.com>
> wrote:
>
>
>
>> On 02-May-2020, at 5:51 AM, Song Liu <songliubrav...@fb.com> wrote:
>>
>> This patch tries to enable PMU sharing. When multiple perf_events are
>> counting the same metric, they can share the hardware PMU counter. We
>> call these events as "compatible events".
>>
>> The PMU sharing are limited to events within the same perf_event_context
>> (ctx). When a event is installed or enabled, search the ctx for compatible
>> events. This is implemented in perf_event_setup_dup(). One of these
>> compatible events are picked as the master (stored in event->dup_master).
>> Similarly, when the event is removed or disabled, perf_event_remove_dup()
>> is used to clean up sharing.
>>
>> If the master event is a cgroup event or a event in a group, it is
>> possible that some slave events are ACTIVE, but the master event is not.
>> To handle this scenario, we introduced PERF_EVENT_STATE_ENABLED. Also,
>> since PMU drivers write into event->count, master event needs another
>> variable (master_count) for the reading of this event.
>>
>> On the critical paths (add, del read), sharing PMU counters doesn't
>> increase the complexity. Helper functions event_pmu_[add|del|read]() are
>> introduced to cover these cases. All these functions have O(1) time
>> complexity.
>>
>> Cc: Peter Zijlstra <pet...@infradead.org>
>> Cc: Arnaldo Carvalho de Melo <a...@redhat.com>
>> Cc: Jiri Olsa <jo...@kernel.org>
>> Cc: Alexey Budankov <alexey.budan...@linux.intel.com>
>> Cc: Namhyung Kim <namhy...@kernel.org>
>> Cc: Tejun Heo <t...@kernel.org>
>> Reported-by: kernel test robot <rong.a.c...@intel.com>
>> Signed-off-by: Song Liu <songliubrav...@fb.com>
>>
>> ---
>> Changes in v13:
>> Fix memory ordering in perf_event_exit_dup_master and perf_event_count.
>> Remove test code in perf_event_can_share().
>>
>> Changes in v12:
>> Add perf_event->dup_active_list to fix rdpmc. (kernel test robot)
>> Fix event reset. (kernel test robot)
>> Do not consider sharing when the perf event is disabled.
>>
>> Changes in v11:
>> Fold in major fixes by Peter.
>> In perf_event_remove_dup(), del() old master before add() new master.
>>
>> Changes in v10:
>> Simplify logic that calls perf_event_setup_dup() and
>> perf_event_remove_dup(). (Peter)
>> Other small fixes. (Peter)
>>
>> Changes in v9:
>> Avoid ctx_resched() on remove/disable event (Peter).
>> Compare the whole perf_event_attr in perf_event_compatible().
>> Small fixes/improvements (Peter).
>>
>> Changes in v8:
>> Fix issues with task event (Jiri).
>> Fix issues with event inherit.
>> Fix mmap'ed events, i.e. perf test 4 (kernel test bot).
>>
>> Changes in v7:
>> Major rewrite to avoid allocating extra master event.
>> (cherry picked from commit 8b98afc0ec100b017a5e80c184809939d4f01f8d)
>>
>> fix perf_event_count()
>> ---
>> arch/x86/events/core.c | 7 +
>> include/linux/perf_event.h | 22 +-
>> kernel/events/core.c | 422 ++++++++++++++++++++++++++++++++++---
>> 3 files changed, 416 insertions(+), 35 deletions(-)
>>
>> diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
>> index 9e63ee50b19a..a245cac31a19 100644
>> --- a/arch/x86/events/core.c
>> +++ b/arch/x86/events/core.c
>> @@ -2345,6 +2345,11 @@ static int x86_pmu_aux_output_match(struct perf_event
>> *event)
>> return 0;
>> }
>>
>> +static void x86_copy_hw_config(struct perf_event *old, struct perf_event
>> *new)
>> +{
>> + new->hw.idx = old->hw.idx;
>> +}
>> +
>> static struct pmu pmu = {
>> .pmu_enable = x86_pmu_enable,
>> .pmu_disable = x86_pmu_disable,
>> @@ -2373,6 +2378,8 @@ static struct pmu pmu = {
>> .check_period = x86_pmu_check_period,
>>
>> .aux_output_match = x86_pmu_aux_output_match,
>> +
>> + .copy_hw_config = x86_copy_hw_config,
>> };
>>
>> void arch_perf_update_userpage(struct perf_event *event,
>> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
>> index 87e21681759c..1306fbd920fd 100644
>> --- a/include/linux/perf_event.h
>> +++ b/include/linux/perf_event.h
>> @@ -503,6 +503,13 @@ struct pmu {
>> * Check period value for PERF_EVENT_IOC_PERIOD ioctl.
>> */
>> int (*check_period) (struct perf_event *event, u64 value);
>> /* optional */
>> +
>> + /*
>> + * Copy hw configuration from one event to another. This is used
>> + * to make switching master faster in PMC sharing.
>> + */
>> + void (*copy_hw_config) (struct perf_event *old,
>> + struct perf_event *new); /* optional */
>> };
>>
>> enum perf_addr_filter_action_t {
>> @@ -552,6 +559,10 @@ struct perf_addr_filter_range {
>>
>> /**
>> * enum perf_event_state - the states of an event:
>> + *
>> + * PERF_EVENT_STATE_ENABLED: Special state for PMC sharing: the hw
>> PMC
>> + * is enabled, but this event is not counting.
>> + * See perf_event_init_dup_master().
>> */
>> enum perf_event_state {
>> PERF_EVENT_STATE_DEAD = -4,
>> @@ -559,7 +570,8 @@ enum perf_event_state {
>> PERF_EVENT_STATE_ERROR = -2,
>> PERF_EVENT_STATE_OFF = -1,
>> PERF_EVENT_STATE_INACTIVE = 0,
>> - PERF_EVENT_STATE_ACTIVE = 1,
>> + PERF_EVENT_STATE_ENABLED = 1,
>> + PERF_EVENT_STATE_ACTIVE = 2,
>> };
>>
>> struct file;
>> @@ -645,6 +657,7 @@ struct perf_event {
>> int group_caps;
>>
>> struct perf_event *group_leader;
>> + struct perf_event *dup_master; /* for PMU sharing */
>> struct pmu *pmu;
>> void *pmu_private;
>>
>> @@ -762,6 +775,13 @@ struct perf_event {
>> void *security;
>> #endif
>> struct list_head sb_list;
>> +
>> + int dup_active;
>> + /* See event_pmu_read_dup() */
>> + local64_t dup_count;
>> + /* See perf_event_init_dup_master() */
>> + local64_t master_count;
>> + struct list_head dup_active_list;
>> #endif /* CONFIG_PERF_EVENTS */
>> };
>>
>> diff --git a/kernel/events/core.c b/kernel/events/core.c
>> index 206dd29c3c6c..40c8b15407b7 100644
>> --- a/kernel/events/core.c
>> +++ b/kernel/events/core.c
>> @@ -1002,7 +1002,6 @@ perf_cgroup_event_enable(struct perf_event *event,
>> struct perf_event_context *ct
>> */
>> cpuctx = container_of(ctx, struct perf_cpu_context, ctx);
>>
>> - pr_info("%s cpu %d\n", __func__, smp_processor_id());
>> /*
>> * Since setting cpuctx->cgrp is conditional on the current @cgrp
>> * matching the event's cgroup, we must do this for every new event,
>> @@ -1012,8 +1011,6 @@ perf_cgroup_event_enable(struct perf_event *event,
>> struct perf_event_context *ct
>> if (ctx->is_active && !cpuctx->cgrp) {
>> struct perf_cgroup *cgrp = perf_cgroup_from_task(current, ctx);
>>
>> - pr_info("%s cpu %d cgrp %px\n", __func__, smp_processor_id(),
>> - cgrp);
>
> Hi Song Liu,
>
> I had problem in trying to apply this patch on latest upstream. Example, the
> `pr_info` in perf_cgroup_event_enable. Looks like there were some local
> changes on top of which this patch was created. Could you please confirm to
> make sure there are no other changes missing.
Sorry for the confusion. You are right that those two pr_info() are from a local
commit. I pushed latest version to
https://git.kernel.org/pub/scm/linux/kernel/git/song/linux.git/log/?h=pmu-share
Please let me know if you have problem with it.
Thanks,
Song
