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perf/core: Invert perf_read_group() loops

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In order to enable the use of perf_event_read(.group = true), we need
to invert the sibling-child loop nesting of perf_read_group().

Currently we iterate the child list for each sibling, this precludes
using group reads. Flip things around so we iterate each group for
each child.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
[ Made the patch compile and things. ]
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: http://lkml.kernel.org/r/1441336073-22750-7-git-send-email-sukadev@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2015-09-03 20:07:49 -07:00 committed by Ingo Molnar
parent 0492d4c5b8
commit fa8c269353
1 changed files with 58 additions and 33 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

91
kernel/events/core.c
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@ -3862,50 +3862,75 @@ u64 perf_event_read_value(struct perf_event *event, u64 *enabled, u64 *running)
}
EXPORT_SYMBOL_GPL(perf_event_read_value);
static int perf_read_group(struct perf_event *event,
u64 read_format, char __user *buf)
static void __perf_read_group_add(struct perf_event *leader,
u64 read_format, u64 *values)
{
struct perf_event *leader = event->group_leader, *sub;
struct perf_event_context *ctx = leader->ctx;
int n = 0, size = 0, ret;
u64 count, enabled, running;
u64 values[5];
struct perf_event *sub;
int n = 1; /* skip @nr */
lockdep_assert_held(&ctx->mutex);
perf_event_read(leader, true);
count = perf_event_read_value(leader, &enabled, &running);
/*
* Since we co-schedule groups, {enabled,running} times of siblings
* will be identical to those of the leader, so we only publish one
* set.
*/
if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED) {
values[n++] += leader->total_time_enabled +
atomic64_read(&leader->child_total_time_enabled);
}
values[n++] = 1 + leader->nr_siblings;
if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
values[n++] = enabled;
if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
values[n++] = running;
values[n++] = count;
if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING) {
values[n++] += leader->total_time_running +
atomic64_read(&leader->child_total_time_running);
}
/*
* Write {count,id} tuples for every sibling.
*/
values[n++] += perf_event_count(leader);
if (read_format & PERF_FORMAT_ID)
values[n++] = primary_event_id(leader);
size = n * sizeof(u64);
if (copy_to_user(buf, values, size))
return -EFAULT;
ret = size;
list_for_each_entry(sub, &leader->sibling_list, group_entry) {
n = 0;
values[n++] = perf_event_read_value(sub, &enabled, &running);
values[n++] += perf_event_count(sub);
if (read_format & PERF_FORMAT_ID)
values[n++] = primary_event_id(sub);
size = n * sizeof(u64);
if (copy_to_user(buf + ret, values, size)) {
return -EFAULT;
}
ret += size;
}
}
static int perf_read_group(struct perf_event *event,
u64 read_format, char __user *buf)
{
struct perf_event *leader = event->group_leader, *child;
struct perf_event_context *ctx = leader->ctx;
int ret = event->read_size;
u64 *values;
lockdep_assert_held(&ctx->mutex);
values = kzalloc(event->read_size, GFP_KERNEL);
if (!values)
return -ENOMEM;
values[0] = 1 + leader->nr_siblings;
/*
* By locking the child_mutex of the leader we effectively
* lock the child list of all siblings.. XXX explain how.
*/
mutex_lock(&leader->child_mutex);
__perf_read_group_add(leader, read_format, values);
list_for_each_entry(child, &leader->child_list, child_list)
__perf_read_group_add(child, read_format, values);
mutex_unlock(&leader->child_mutex);
if (copy_to_user(buf, values, event->read_size))
ret = -EFAULT;
kfree(values);
return ret;
}