From 76e1d9047e4edefb8ada20aa90d5762306082bd6 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Mon, 5 Apr 2010 15:35:57 +0200 Subject: perf: Store active software events in a hashlist Each time a software event triggers, we need to walk through the entire list of events from the current cpu and task contexts to retrieve a running perf event that matches. We also need to check a matching perf event is actually counting. This walk is wasteful and makes the event fast path scaling down with a growing number of events running on the same contexts. To solve this, we store the running perf events in a hashlist to get an immediate access to them against their type:event_id when they trigger. v2: - Fix SWEVENT_HLIST_SIZE definition (and re-learn some basic maths along the way) - Only allocate hlist for online cpus, but keep track of the refcount on offline possible cpus too, so that we allocate it if needed when it becomes online. - Drop the kref use as it's not adapted to our tricks anymore. v3: - Fix bad refcount check (address instead of value). Thanks to Eric Dumazet who spotted this. - While exiting cpu, move the hlist release out of the IPI path to lock the hlist mutex sanely. Signed-off-by: Frederic Weisbecker Cc: Peter Zijlstra Cc: Arnaldo Carvalho de Melo Cc: Paul Mackerras Cc: Ingo Molnar --- include/linux/perf_event.h | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'include/linux') diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 6e96cc8225d4..bf896d0b2e9c 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -589,6 +589,14 @@ enum perf_group_flag { PERF_GROUP_SOFTWARE = 0x1, }; +#define SWEVENT_HLIST_BITS 8 +#define SWEVENT_HLIST_SIZE (1 << SWEVENT_HLIST_BITS) + +struct swevent_hlist { + struct hlist_head heads[SWEVENT_HLIST_SIZE]; + struct rcu_head rcu_head; +}; + /** * struct perf_event - performance event kernel representation: */ @@ -597,6 +605,7 @@ struct perf_event { struct list_head group_entry; struct list_head event_entry; struct list_head sibling_list; + struct hlist_node hlist_entry; int nr_siblings; int group_flags; struct perf_event *group_leader; @@ -744,6 +753,9 @@ struct perf_cpu_context { int active_oncpu; int max_pertask; int exclusive; + struct swevent_hlist *swevent_hlist; + struct mutex hlist_mutex; + int hlist_refcount; /* * Recursion avoidance: -- cgit v1.2.3