From 6bde9b6ce0127e2a56228a2071536d422be31336 Mon Sep 17 00:00:00 2001 From: Lin Ming Date: Fri, 23 Apr 2010 13:56:00 +0800 Subject: [PATCH] perf: Add group scheduling transactional APIs Add group scheduling transactional APIs to struct pmu. These APIs will be implemented in arch code, based on Peter's idea as below. > the idea behind hw_perf_group_sched_in() is to not perform > schedulability tests on each event in the group, but to add the group > as a whole and then perform one test. > > Of course, when that test fails, you'll have to roll-back the whole > group again. > > So start_txn (or a better name) would simply toggle a flag in the pmu > implementation that will make pmu::enable() not perform the > schedulablilty test. > > Then commit_txn() will perform the schedulability test (so note the > method has to have a !void return value. > > This will allow us to use the regular > kernel/perf_event.c::group_sched_in() and all the rollback code. > Currently each hw_perf_group_sched_in() implementation duplicates all > the rolllback code (with various bugs). ->start_txn: Start group events scheduling transaction, set a flag to make pmu::enable() not perform the schedulability test, it will be performed at commit time. ->commit_txn: Commit group events scheduling transaction, perform the group schedulability as a whole ->cancel_txn: Stop group events scheduling transaction, clear the flag so pmu::enable() will perform the schedulability test. Reviewed-by: Stephane Eranian Reviewed-by: Frederic Weisbecker Signed-off-by: Lin Ming Cc: David Miller Cc: Paul Mackerras Signed-off-by: Peter Zijlstra LKML-Reference: <1272002160.5707.60.camel@minggr.sh.intel.com> Signed-off-by: Ingo Molnar --- include/linux/perf_event.h | 15 ++++++++++++--- kernel/perf_event.c | 33 ++++++++++++++++++++------------- 2 files changed, 32 insertions(+), 16 deletions(-) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 23cd0057a68..4924c96d7e2 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -547,6 +547,8 @@ struct hw_perf_event { struct perf_event; +#define PERF_EVENT_TXN_STARTED 1 + /** * struct pmu - generic performance monitoring unit */ @@ -557,6 +559,16 @@ struct pmu { void (*stop) (struct perf_event *event); void (*read) (struct perf_event *event); void (*unthrottle) (struct perf_event *event); + + /* + * group events scheduling is treated as a transaction, + * add group events as a whole and perform one schedulability test. + * If test fails, roll back the whole group + */ + + void (*start_txn) (const struct pmu *pmu); + void (*cancel_txn) (const struct pmu *pmu); + int (*commit_txn) (const struct pmu *pmu); }; /** @@ -823,9 +835,6 @@ extern void perf_disable(void); extern void perf_enable(void); extern int perf_event_task_disable(void); extern int perf_event_task_enable(void); -extern int hw_perf_group_sched_in(struct perf_event *group_leader, - struct perf_cpu_context *cpuctx, - struct perf_event_context *ctx); extern void perf_event_update_userpage(struct perf_event *event); extern int perf_event_release_kernel(struct perf_event *event); extern struct perf_event * diff --git a/kernel/perf_event.c b/kernel/perf_event.c index 34659d4085c..bb06382f98e 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -83,14 +83,6 @@ extern __weak const struct pmu *hw_perf_event_init(struct perf_event *event) void __weak hw_perf_disable(void) { barrier(); } void __weak hw_perf_enable(void) { barrier(); } -int __weak -hw_perf_group_sched_in(struct perf_event *group_leader, - struct perf_cpu_context *cpuctx, - struct perf_event_context *ctx) -{ - return 0; -} - void __weak perf_event_print_debug(void) { } static DEFINE_PER_CPU(int, perf_disable_count); @@ -644,15 +636,20 @@ group_sched_in(struct perf_event *group_event, struct perf_cpu_context *cpuctx, struct perf_event_context *ctx) { - struct perf_event *event, *partial_group; + struct perf_event *event, *partial_group = NULL; + const struct pmu *pmu = group_event->pmu; + bool txn = false; int ret; if (group_event->state == PERF_EVENT_STATE_OFF) return 0; - ret = hw_perf_group_sched_in(group_event, cpuctx, ctx); - if (ret) - return ret < 0 ? ret : 0; + /* Check if group transaction availabe */ + if (pmu->start_txn) + txn = true; + + if (txn) + pmu->start_txn(pmu); if (event_sched_in(group_event, cpuctx, ctx)) return -EAGAIN; @@ -667,9 +664,19 @@ group_sched_in(struct perf_event *group_event, } } - return 0; + if (txn) { + ret = pmu->commit_txn(pmu); + if (!ret) { + pmu->cancel_txn(pmu); + + return 0; + } + } group_error: + if (txn) + pmu->cancel_txn(pmu); + /* * Groups can be scheduled in as one unit only, so undo any * partial group before returning: -- 2.20.1