From d6f962b57bfaab62891c7abbf1469212a56d6103 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Sun, 10 Jan 2010 01:25:51 +0100 Subject: [PATCH] perf: Export software-only event group characteristic as a flag Before scheduling an event group, we first check if a group can go on. We first check if the group is made of software only events first, in which case it is enough to know if the group can be scheduled in. For that purpose, we iterate through the whole group, which is wasteful as we could do this check when we add/delete an event to a group. So we create a group_flags field in perf event that can host characteristics from a group of events, starting with a first PERF_GROUP_SOFTWARE flag that reduces the check on the fast path. Signed-off-by: Frederic Weisbecker Acked-by: Peter Zijlstra Cc: Paul Mackerras Cc: Ingo Molnar Cc: Arnaldo Carvalho de Melo --- include/linux/perf_event.h | 5 +++++ kernel/perf_event.c | 30 +++++++++++------------------- 2 files changed, 16 insertions(+), 19 deletions(-) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index cdbc2aa64a0b..c6f812e4d058 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -565,6 +565,10 @@ typedef void (*perf_overflow_handler_t)(struct perf_event *, int, struct perf_sample_data *, struct pt_regs *regs); +enum perf_group_flag { + PERF_GROUP_SOFTWARE = 0x1, +}; + /** * struct perf_event - performance event kernel representation: */ @@ -574,6 +578,7 @@ struct perf_event { struct list_head event_entry; struct list_head sibling_list; int nr_siblings; + int group_flags; struct perf_event *group_leader; struct perf_event *output; const struct pmu *pmu; diff --git a/kernel/perf_event.c b/kernel/perf_event.c index bbebe2832639..eae6ff693604 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -315,9 +315,16 @@ list_add_event(struct perf_event *event, struct perf_event_context *ctx) if (group_leader == event) { struct list_head *list; + if (is_software_event(event)) + event->group_flags |= PERF_GROUP_SOFTWARE; + list = ctx_group_list(event, ctx); list_add_tail(&event->group_entry, list); } else { + if (group_leader->group_flags & PERF_GROUP_SOFTWARE && + !is_software_event(event)) + group_leader->group_flags &= ~PERF_GROUP_SOFTWARE; + list_add_tail(&event->group_entry, &group_leader->sibling_list); group_leader->nr_siblings++; } @@ -372,6 +379,9 @@ list_del_event(struct perf_event *event, struct perf_event_context *ctx) list = ctx_group_list(event, ctx); list_move_tail(&sibling->group_entry, list); sibling->group_leader = sibling; + + /* Inherit group flags from the previous leader */ + sibling->group_flags = event->group_flags; } } @@ -699,24 +709,6 @@ group_error: return -EAGAIN; } -/* - * Return 1 for a group consisting entirely of software events, - * 0 if the group contains any hardware events. - */ -static int is_software_only_group(struct perf_event *leader) -{ - struct perf_event *event; - - if (!is_software_event(leader)) - return 0; - - list_for_each_entry(event, &leader->sibling_list, group_entry) - if (!is_software_event(event)) - return 0; - - return 1; -} - /* * Work out whether we can put this event group on the CPU now. */ @@ -727,7 +719,7 @@ static int group_can_go_on(struct perf_event *event, /* * Groups consisting entirely of software events can always go on. */ - if (is_software_only_group(event)) + if (event->group_flags & PERF_GROUP_SOFTWARE) return 1; /* * If an exclusive group is already on, no other hardware -- 2.30.2