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perf_counter tools: Handle lost events

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Make use of the new ->data_tail mechanism to tell kernel-space
about user-space draining the data stream. Emit lost events
(and display them) if they happen.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra
2009-06-18 11:40:28 +02:00
committed by Ingo Molnar
parent 43a21ea81a
commit 9d91a6f7a4
2 changed files with 44 additions and 5 deletions
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20
tools/perf/builtin-record.c
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@ -78,10 +78,10 @@ struct mmap_data {
static struct mmap_data mmap_array[MAX_NR_CPUS][MAX_COUNTERS];
static unsigned int mmap_read_head(struct mmap_data *md)
static unsigned long mmap_read_head(struct mmap_data *md)
{
struct perf_counter_mmap_page *pc = md->base;
int head;
long head;
head = pc->data_head;
rmb();
@ -89,6 +89,17 @@ static unsigned int mmap_read_head(struct mmap_data *md)
return head;
}
static void mmap_write_tail(struct mmap_data *md, unsigned long tail)
{
struct perf_counter_mmap_page *pc = md->base;
/*
* ensure all reads are done before we write the tail out.
*/
/* mb(); */
pc->data_tail = tail;
}
static void mmap_read(struct mmap_data *md)
{
unsigned int head = mmap_read_head(md);
@ -109,7 +120,7 @@ static void mmap_read(struct mmap_data *md)
* In either case, truncate and restart at head.
*/
diff = head - old;
if (diff > md->mask / 2 || diff < 0) {
if (diff < 0) {
struct timeval iv;
unsigned long msecs;
@ -167,6 +178,7 @@ static void mmap_read(struct mmap_data *md)
}
md->prev = old;
mmap_write_tail(md, old);
}
static volatile int done = 0;
@ -424,7 +436,7 @@ try_again:
mmap_array[nr_cpu][counter].prev = 0;
mmap_array[nr_cpu][counter].mask = mmap_pages*page_size - 1;
mmap_array[nr_cpu][counter].base = mmap(NULL, (mmap_pages+1)*page_size,
PROT_READ, MAP_SHARED, fd[nr_cpu][counter], 0);
PROT_READ|PROT_WRITE, MAP_SHARED, fd[nr_cpu][counter], 0);
if (mmap_array[nr_cpu][counter].base == MAP_FAILED) {
error("failed to mmap with %d (%s)\n", errno, strerror(errno));
exit(-1);