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From: Peter Zijlstra on 21 May 2010 05:20
It seems a waste of space to create a buffer per event, share it per-cpu.

Signed-off-by: Peter Zijlstra <a.p.zijlstra(a)chello.nl>
---
tools/perf/builtin-record.c | 52 +++++++++++++++++++++++---------------------
1 file changed, 28 insertions(+), 24 deletions(-)

Index: linux-2.6/tools/perf/builtin-record.c
===================================================================
--- linux-2.6.orig/tools/perf/builtin-record.c
+++ linux-2.6/tools/perf/builtin-record.c
@@ -85,7 +85,7 @@ struct mmap_data {
unsigned int prev;
};

-static struct mmap_data *mmap_array[MAX_NR_CPUS][MAX_COUNTERS];
+static struct mmap_data mmap_array[MAX_NR_CPUS];

static unsigned long mmap_read_head(struct mmap_data *md)
{
@@ -380,18 +380,29 @@ try_again:
if (group && group_fd == -1)
group_fd = fd[nr_cpu][counter][thread_index];

- event_array[nr_poll].fd = fd[nr_cpu][counter][thread_index];
- event_array[nr_poll].events = POLLIN;
- nr_poll++;
-
- mmap_array[nr_cpu][counter][thread_index].counter = counter;
- mmap_array[nr_cpu][counter][thread_index].prev = 0;
- mmap_array[nr_cpu][counter][thread_index].mask = mmap_pages*page_size - 1;
- mmap_array[nr_cpu][counter][thread_index].base = mmap(NULL, (mmap_pages+1)*page_size,
- PROT_READ|PROT_WRITE, MAP_SHARED, fd[nr_cpu][counter][thread_index], 0);
- if (mmap_array[nr_cpu][counter][thread_index].base == MAP_FAILED) {
- error("failed to mmap with %d (%s)\n", errno, strerror(errno));
- exit(-1);
+ if (counter || thread_index) {
+ ret = ioctl(fd[nr_cpu][counter][thread_index],
+ PERF_EVENT_IOC_SET_OUTPUT,
+ fd[nr_cpu][0][0]);
+ if (ret) {
+ error("failed to set output: %d (%s)\n", errno,
+ strerror(errno));
+ exit(-1);
+ }
+ } else {
+ mmap_array[nr_cpu].counter = counter;
+ mmap_array[nr_cpu].prev = 0;
+ mmap_array[nr_cpu].mask = mmap_pages*page_size - 1;
+ mmap_array[nr_cpu].base = mmap(NULL, (mmap_pages+1)*page_size,
+ PROT_READ|PROT_WRITE, MAP_SHARED, fd[nr_cpu][counter][thread_index], 0);
+ if (mmap_array[nr_cpu].base == MAP_FAILED) {
+ error("failed to mmap with %d (%s)\n", errno, strerror(errno));
+ exit(-1);
+ }
+
+ event_array[nr_poll].fd = fd[nr_cpu][counter][thread_index];
+ event_array[nr_poll].events = POLLIN;
+ nr_poll++;
}

if (filter != NULL) {
@@ -492,16 +503,11 @@ static struct perf_event_header finished

static void mmap_read_all(void)
{
- int i, counter, thread;
+ int i;

for (i = 0; i < nr_cpu; i++) {
- for (counter = 0; counter < nr_counters; counter++) {
- for (thread = 0; thread < thread_num; thread++) {
- if (mmap_array[i][counter][thread].base)
- mmap_read(&mmap_array[i][counter][thread]);
- }
-
- }
+ if (mmap_array[i].base)
+ mmap_read(&mmap_array[i]);
}

if (perf_header__has_feat(&session->header, HEADER_TRACE_INFO))
@@ -876,9 +882,7 @@ int cmd_record(int argc, const char **ar
for (i = 0; i < MAX_NR_CPUS; i++) {
for (j = 0; j < MAX_COUNTERS; j++) {
fd[i][j] = malloc(sizeof(int)*thread_num);
- mmap_array[i][j] = zalloc(
- sizeof(struct mmap_data)*thread_num);
- if (!fd[i][j] || !mmap_array[i][j])
+ if (!fd[i][j])
return -ENOMEM;
}
}


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Prev: [PATCH 06/10] perf: Fix wakeup storm for RO mmap()s
Next: [PATCH 04/10] perf-record: Remove -M