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perf evlist: Steal mmap reading routine from 'perf top'

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Will be used in the upcoming 'perf test' entry for the evlist mmap
routines.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Arnaldo Carvalho de Melo
2011-01-15 10:40:59 -02:00
parent 98d77b7850
commit 04391debc3
3 changed files with 69 additions and 53 deletions
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62
tools/perf/util/evlist.c
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@@ -95,3 +95,65 @@ struct perf_evsel *perf_evlist__id2evsel(struct perf_evlist *evlist, u64 id)
return sid->evsel;
return NULL;
}
event_t *perf_evlist__read_on_cpu(struct perf_evlist *evlist, int cpu)
{
/* XXX Move this to perf.c, making it generally available */
unsigned int page_size = sysconf(_SC_PAGE_SIZE);
struct perf_mmap *md = &evlist->mmap[cpu];
unsigned int head = perf_mmap__read_head(md);
unsigned int old = md->prev;
unsigned char *data = md->base + page_size;
event_t *event = NULL;
int diff;
/*
* If we're further behind than half the buffer, there's a chance
* the writer will bite our tail and mess up the samples under us.
*
* If we somehow ended up ahead of the head, we got messed up.
*
* In either case, truncate and restart at head.
*/
diff = head - old;
if (diff > md->mask / 2 || diff < 0) {
fprintf(stderr, "WARNING: failed to keep up with mmap data.\n");
/*
* head points to a known good entry, start there.
*/
old = head;
}
if (old != head) {
size_t size;
event = (event_t *)&data[old & md->mask];
size = event->header.size;
/*
* Event straddles the mmap boundary -- header should always
* be inside due to u64 alignment of output.
*/
if ((old & md->mask) + size != ((old + size) & md->mask)) {
unsigned int offset = old;
unsigned int len = min(sizeof(*event), size), cpy;
void *dst = &evlist->event_copy;
do {
cpy = min(md->mask + 1 - (offset & md->mask), len);
memcpy(dst, &data[offset & md->mask], cpy);
offset += cpy;
dst += cpy;
len -= cpy;
} while (len);
event = &evlist->event_copy;
}
old += size;
}
md->prev = old;
return event;
}