On Thu, 2010-05-20 at 09:33 +0800, Corey Ashford wrote:On 5/19/2010 6:17 PM, Lin Ming wrote:On Thu, 2010-05-20 at 02:18 +0800, Corey Ashford wrote:
On 5/18/2010 6:49 PM, Lin Ming wrote:Just a temporary patch to show how to use the pmu sysfs interface...
Signed-off-by: Lin Ming<ming.m.lin@xxxxxxxxx>
---
tools/perf/builtin-top.c | 13 +++++++++++++
1 files changed, 13 insertions(+), 0 deletions(-)
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index adc179d..eaa9405 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -1206,6 +1206,7 @@ static void start_counter(int i, int counter)
struct perf_event_attr *attr;
int cpu;
int thread_index;
+ int sys_fd;
cpu = profile_cpu;
if (target_tid == -1&& profile_cpu == -1)
@@ -1226,9 +1227,21 @@ static void start_counter(int i, int counter)
for (thread_index = 0; thread_index< thread_num; thread_index++) {
try_again:
+ /*
+ * This is just an ugly demo of how to use the sysfs interface.
+ * You can also parse the<event-name> and open sys file as,
+ * sys_fd = open("/sys/devices/system/cpu/events/<event-name>/event_source/id", O_RDONLY);
+ */
In this above case, does this sys_fd also specify the event I am going to open, in addition to its event source? I'd assume not since event_source is a symlink to /sys/devices/system/cpu/event_source (right?)
Right, this sys_fd only specifies the event source.
How do I specify the exact event id via the sysfs interface?
/sys/devices/system/cpu/events/<event-name>/id
But in this patch series, the event id sysfs interface is not used yet.
So, I would open that id and then read the id code and place it in attr->config or maybe place
the fd into attr (somewhere) ?
Place the id code in attr->config.
We also need to take into account event "attributes" - other data that is needed to configure a specific event. For example, think about a memory controller which has a PMU can count events in a particular memory range; we need to be able to supply the memory range somehow, and I don't think that can be accomplished by passing in the fd of a sysfs file that we've opened.
Each event is a directory in the sysfs, so we can put all the event
"attributes" under it.
For your example,
/sys/devices/system/node/events/<event-name>/id
/sys/devices/system/node/events/<event-name>/memory_range
....
Then we can read these attributes and pass the value into the syscall.