[tip:perf/core] perf: Default PMU ops

tip-bot for Peter Zijlstra
2010-09-09T19:50:18Z

Commit-ID: ad5133b7030d04ce7701aa7cbe98f561347c79c2
Gitweb: http://git.kernel.org/tip/ad5133b7030d04ce7701aa7cbe98f561347c79c2
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Tue, 15 Jun 2010 12:22:39 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Thu, 9 Sep 2010 20:46:30 +0200

perf: Default PMU ops

Provide default implementations for the pmu txn methods, this
allows us to remove some conditional code.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: paulus <paulus@samba.org>
Cc: stephane eranian <eranian@googlemail.com>
Cc: Robert Richter <robert.richter@amd.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: Lin Ming <ming.m.lin@intel.com>
Cc: Yanmin <yanmin_zhang@linux.intel.com>
Cc: Deng-Cheng Zhu <dengcheng.zhu@gmail.com>
Cc: David Miller <davem@davemloft.net>
Cc: Michael Cree <mcree@orcon.net.nz>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
include/linux/perf_event.h | 10 +++---
kernel/perf_event.c | 64 +++++++++++++++++++++++++++++++++++--------
2 files changed, 57 insertions(+), 17 deletions(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 6abf103..bf85733 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -565,8 +565,8 @@ struct pmu {

int *pmu_disable_count;

- void (*pmu_enable) (struct pmu *pmu);
- void (*pmu_disable) (struct pmu *pmu);
+ void (*pmu_enable) (struct pmu *pmu); /* optional */
+ void (*pmu_disable) (struct pmu *pmu); /* optional */

/*
* Should return -ENOENT when the @event doesn't match this PMU.
@@ -590,19 +590,19 @@ struct pmu {
* Start the transaction, after this ->enable() doesn't need to
* do schedulability tests.
*/
- void (*start_txn) (struct pmu *pmu);
+ void (*start_txn) (struct pmu *pmu); /* optional */
/*
* If ->start_txn() disabled the ->enable() schedulability test
* then ->commit_txn() is required to perform one. On success
* the transaction is closed. On error the transaction is kept
* open until ->cancel_txn() is called.
*/
- int (*commit_txn) (struct pmu *pmu);
+ int (*commit_txn) (struct pmu *pmu); /* optional */
/*
* Will cancel the transaction, assumes ->disable() is called
* for each successfull ->enable() during the transaction.
*/
- void (*cancel_txn) (struct pmu *pmu);
+ void (*cancel_txn) (struct pmu *pmu); /* optional */
};

/**
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 5ed0c06..8ef4ba3 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -674,21 +674,14 @@ group_sched_in(struct perf_event *group_event,
{
struct perf_event *event, *partial_group = NULL;
struct pmu *pmu = group_event->pmu;
- bool txn = false;

if (group_event->state == PERF_EVENT_STATE_OFF)
return 0;

- /* Check if group transaction availabe */
- if (pmu->start_txn)
- txn = true;
-
- if (txn)
- pmu->start_txn(pmu);
+ pmu->start_txn(pmu);

if (event_sched_in(group_event, cpuctx, ctx)) {
- if (txn)
- pmu->cancel_txn(pmu);
+ pmu->cancel_txn(pmu);
return -EAGAIN;
}

@@ -702,7 +695,7 @@ group_sched_in(struct perf_event *group_event,
}
}

- if (!txn || !pmu->commit_txn(pmu))
+ if (!pmu->commit_txn(pmu))
return 0;

group_error:
@@ -717,8 +710,7 @@ group_error:
}
event_sched_out(group_event, cpuctx, ctx);

- if (txn)
- pmu->cancel_txn(pmu);
+ pmu->cancel_txn(pmu);

return -EAGAIN;
}
@@ -4965,6 +4957,31 @@ static LIST_HEAD(pmus);
static DEFINE_MUTEX(pmus_lock);
static struct srcu_struct pmus_srcu;

+static void perf_pmu_nop_void(struct pmu *pmu)
+{
+}
+
+static int perf_pmu_nop_int(struct pmu *pmu)
+{
+ return 0;
+}
+
+static void perf_pmu_start_txn(struct pmu *pmu)
+{
+ perf_pmu_disable(pmu);
+}
+
+static int perf_pmu_commit_txn(struct pmu *pmu)
+{
+ perf_pmu_enable(pmu);
+ return 0;
+}
+
+static void perf_pmu_cancel_txn(struct pmu *pmu)
+{
+ perf_pmu_enable(pmu);
+}
+
int perf_pmu_register(struct pmu *pmu)
{
int ret;
@@ -4974,6 +4991,29 @@ int perf_pmu_register(struct pmu *pmu)
pmu->pmu_disable_count = alloc_percpu(int);
if (!pmu->pmu_disable_count)
goto unlock;
+
+ if (!pmu->start_txn) {
+ if (pmu->pmu_enable) {
+ /*
+ * If we have pmu_enable/pmu_disable calls, install
+ * transaction stubs that use that to try and batch
+ * hardware accesses.
+ */
+ pmu->start_txn = perf_pmu_start_txn;
+ pmu->commit_txn = perf_pmu_commit_txn;
+ pmu->cancel_txn = perf_pmu_cancel_txn;
+ } else {
+ pmu->start_txn = perf_pmu_nop_void;
+ pmu->commit_txn = perf_pmu_nop_int;
+ pmu->cancel_txn = perf_pmu_nop_void;
+ }
+ }
+
+ if (!pmu->pmu_enable) {
+ pmu->pmu_enable = perf_pmu_nop_void;
+ pmu->pmu_disable = perf_pmu_nop_void;
+ }
+
list_add_rcu(&pmu->entry, &pmus);
ret = 0;