Re: [PATCH v2]: perf/core: addressing 4x slowdown during per-process, profiling of STREAM benchmark on Intel Xeon Phi

Alexey Budankov
2017-05-29T09:15:27Z

On 29.05.2017 10:46, Peter Zijlstra wrote:
> On Sat, May 27, 2017 at 02:19:51PM +0300, Alexey Budankov wrote:
>> @@ -571,6 +587,27 @@ struct perf_event {
>> * either sufficies for read.
>> */
>> struct list_head group_entry;
>> + /*
>> + * Node on the pinned or flexible tree located at the event context;
>> + * the node may be empty in case its event is not directly attached
>> + * to the tree but to group_list list of the event directly
>> + * attached to the tree;
>> + */
>> + struct rb_node group_node;
>> + /*
>> + * List keeps groups allocated for the same cpu;
>> + * the list may be empty in case its event is not directly
>> + * attached to the tree but to group_list list of the event directly
>> + * attached to the tree;
>> + */
>> + struct list_head group_list;
>> + /*
>> + * Entry into the group_list list above;
>> + * the entry may be attached to the self group_list list above
>> + * in case the event is directly attached to the pinned or
>> + * flexible tree;
>> + */
>> + struct list_head group_list_entry;
>> struct list_head sibling_list;
>>
>> /*
>
>> @@ -742,7 +772,17 @@ struct perf_event_context {
>>
>> struct list_head active_ctx_list;
>> struct list_head pinned_groups;
>> + /*
>> + * Cpu tree for pinned groups; keeps event's group_node nodes
>> + * of attached flexible groups;
>> + */
>> + struct rb_root pinned_tree;
>> struct list_head flexible_groups;
>> + /*
>> + * Cpu tree for flexible groups; keeps event's group_node nodes
>> + * of attached flexible groups;
>> + */
>> + struct rb_root flexible_tree;
>> struct list_head event_list;
>> int nr_events;
>> int nr_active;
>> @@ -758,6 +798,7 @@ struct perf_event_context {
>> */
>> u64 time;
>> u64 timestamp;
>> + struct perf_event_tstamp tstamp_data;
>>
>> /*
>> * These fields let us detect when two contexts have both
>
>
> So why do we now have a list _and_ a tree for the same entries?
We need groups list to iterate through all groups configured for
collection and we need the tree to quickly iterate through the groups
allocated for a particular CPU only.
>
>

-Alexey