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SubjectRe: [PATCH v7 1/2] perf/core: use rb trees for pinned/flexible groups
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On 23.08.2017 14:17, Alexander Shishkin wrote:
> Alexey Budankov <alexey.budankov@linux.intel.com> writes:
>
>> @@ -3091,61 +3231,55 @@ static void cpu_ctx_sched_out(struct perf_cpu_context *cpuctx,
>> }
>>
>> static void
>> -ctx_pinned_sched_in(struct perf_event_context *ctx,
>> - struct perf_cpu_context *cpuctx)
>> +ctx_pinned_sched_in(struct perf_event *event,
>> + struct perf_cpu_context *cpuctx,
>> + struct perf_event_context *ctx)
>
> If you're doing this, you also need to rename the function, because it
> now schedules in one event and not a context. But better just keep it as
> is.
>
>> {
>> - struct perf_event *event;
>> -
>> - list_for_each_entry(event, &ctx->pinned_groups, group_entry) {
>
> Why not put your new iterator here in place of the old one, instead of
> moving things around? Because what follows is hard to read and is also
> completely unnecessary:
>
>> - if (event->state <= PERF_EVENT_STATE_OFF)
>> - continue;
>> - if (!event_filter_match(event))
>> - continue;
>> + if (event->state <= PERF_EVENT_STATE_OFF)
>> + return;
>> + if (!event_filter_match(event))
>> + return;
>
> like this,
>
>>
>> - /* may need to reset tstamp_enabled */
>> - if (is_cgroup_event(event))
>> - perf_cgroup_mark_enabled(event, ctx);
>> + /* may need to reset tstamp_enabled */
>> + if (is_cgroup_event(event))
>> + perf_cgroup_mark_enabled(event, ctx);
>
> or this
>
>>
>> - if (group_can_go_on(event, cpuctx, 1))
>> - group_sched_in(event, cpuctx, ctx);
>> + if (group_can_go_on(event, cpuctx, 1))
>> + group_sched_in(event, cpuctx, ctx);
>
> etc, etc.
>
>> @@ -3156,7 +3290,8 @@ ctx_sched_in(struct perf_event_context *ctx,
>> struct task_struct *task)
>> {
>> int is_active = ctx->is_active;
>> - u64 now;
>
> Why?

Shortened the scope/span/life time of this variable.
Declared, defined and initialized closer to the place of employment.

>
>> + struct perf_event *event;
>> + struct rb_node *node;
>>
>> lockdep_assert_held(&ctx->lock);
>>
>> @@ -3175,7 +3310,7 @@ ctx_sched_in(struct perf_event_context *ctx,
>>
>> if (is_active & EVENT_TIME) {
>> /* start ctx time */
>> - now = perf_clock();
>> + u64 now = perf_clock();
>
> Why?>
>> ctx->timestamp = now;
>> perf_cgroup_set_timestamp(task, ctx);
>> }
>> @@ -3185,11 +3320,19 @@ ctx_sched_in(struct perf_event_context *ctx,
>> * in order to give them the best chance of going on.
>> */
>> if (is_active & EVENT_PINNED)
>> - ctx_pinned_sched_in(ctx, cpuctx);
>> + perf_event_groups_for_each(event, node,
>> + &ctx->pinned_groups, group_node,
>> + group_list, group_entry)
>> + ctx_pinned_sched_in(event, cpuctx, ctx);
>
> So this perf_event_groups_for_each() can just move into
> ctx_*_sched_in(), can't it?

Yes. Makes sense. Addressed it in v8. Thanks!

>
> Regards,
> --
> Alex
>

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