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Subject[PATCH 1/2] perf tools: Add struct ordered_events_buffer layer
Date
When ordering events, we use preallocated buffers to store separated
events. Those buffers currently don't have their own struct, but since
they are basically array of 'struct ordered_event' objects, we use the
first event to hold buffers data - list head, that holds all buffers
together:

struct ordered_events {
...
struct ordered_event *buffer;
...
};

struct ordered_event {
u64 timestamp;
u64 file_offset;
union perf_event *event;
struct list_head list;
};

This is quite convoluted and error prone as demonstrated by
free-ing issue discovered and fixed by Stephane in here [1].

This patch adds the 'struct ordered_events_buffer' object,
that holds the buffer data and frees it up properly.

[1] - https://marc.info/?l=linux-kernel&m=153376761329335&w=2

Reported-and-tested-by: Stephane Eranian <eranian@google.com>
Tested-by: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-qrkcqm5m1sugy4q83pfn5a1r@git.kernel.org
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
tools/perf/util/ordered-events.c | 83 +++++++++++++++++++++++++++-----
tools/perf/util/ordered-events.h | 37 ++++++++------
2 files changed, 91 insertions(+), 29 deletions(-)

diff --git a/tools/perf/util/ordered-events.c b/tools/perf/util/ordered-events.c
index bad9e0296e9a..87171e8fd70d 100644
--- a/tools/perf/util/ordered-events.c
+++ b/tools/perf/util/ordered-events.c
@@ -80,14 +80,20 @@ static union perf_event *dup_event(struct ordered_events *oe,
return oe->copy_on_queue ? __dup_event(oe, event) : event;
}

-static void free_dup_event(struct ordered_events *oe, union perf_event *event)
+static void __free_dup_event(struct ordered_events *oe, union perf_event *event)
{
- if (event && oe->copy_on_queue) {
+ if (event) {
oe->cur_alloc_size -= event->header.size;
free(event);
}
}

+static void free_dup_event(struct ordered_events *oe, union perf_event *event)
+{
+ if (oe->copy_on_queue)
+ __free_dup_event(oe, event);
+}
+
#define MAX_SAMPLE_BUFFER (64 * 1024 / sizeof(struct ordered_event))
static struct ordered_event *alloc_event(struct ordered_events *oe,
union perf_event *event)
@@ -100,15 +106,43 @@ static struct ordered_event *alloc_event(struct ordered_events *oe,
if (!new_event)
return NULL;

+ /*
+ * We maintain following scheme of buffers for ordered
+ * event allocation:
+ *
+ * to_free list -> buffer1 (64K)
+ * buffer2 (64K)
+ * ...
+ *
+ * Each buffer keeps an array of ordered events objects:
+ * buffer -> event[0]
+ * event[1]
+ * ...
+ *
+ * Each allocated ordered event is linked to one of
+ * following lists:
+ * - time ordered list 'events'
+ * - list of currently removed events 'cache'
+ *
+ * Allocation of the ordered event uses following order
+ * to get the memory:
+ * - use recently removed object from 'cache' list
+ * - use available object in current allocation buffer
+ * - allocate new buffer if the current buffer is full
+ *
+ * Removal of ordered event object moves it from events to
+ * the cache list.
+ */
if (!list_empty(cache)) {
new = list_entry(cache->next, struct ordered_event, list);
list_del(&new->list);
} else if (oe->buffer) {
- new = oe->buffer + oe->buffer_idx;
+ new = &oe->buffer->event[oe->buffer_idx];
if (++oe->buffer_idx == MAX_SAMPLE_BUFFER)
oe->buffer = NULL;
} else if (oe->cur_alloc_size < oe->max_alloc_size) {
- size_t size = MAX_SAMPLE_BUFFER * sizeof(*new);
+ size_t size = sizeof(*oe->buffer) +
+ MAX_SAMPLE_BUFFER * sizeof(*new);

oe->buffer = malloc(size);
if (!oe->buffer) {
@@ -122,11 +156,11 @@ static struct ordered_event *alloc_event(struct ordered_events *oe,
oe->cur_alloc_size += size;
list_add(&oe->buffer->list, &oe->to_free);

- /* First entry is abused to maintain the to_free list. */
- oe->buffer_idx = 2;
- new = oe->buffer + 1;
+ oe->buffer_idx = 1;
+ new = &oe->buffer->event[0];
} else {
pr("allocation limit reached %" PRIu64 "B\n", oe->max_alloc_size);
+ return NULL;
}

new->event = new_event;
@@ -300,15 +334,38 @@ void ordered_events__init(struct ordered_events *oe, ordered_events__deliver_t d
oe->deliver = deliver;
}

+static void
+ordered_events_buffer__free(struct ordered_events_buffer *buffer,
+ unsigned int max, struct ordered_events *oe)
+{
+ if (oe->copy_on_queue) {
+ unsigned int i;
+
+ for (i = 0; i < max; i++)
+ __free_dup_event(oe, buffer->event[i].event);
+ }
+
+ free(buffer);
+}
+
void ordered_events__free(struct ordered_events *oe)
{
- while (!list_empty(&oe->to_free)) {
- struct ordered_event *event;
+ struct ordered_events_buffer *buffer, *tmp;

- event = list_entry(oe->to_free.next, struct ordered_event, list);
- list_del(&event->list);
- free_dup_event(oe, event->event);
- free(event);
+ if (list_empty(&oe->to_free))
+ return;
+
+ /*
+ * Current buffer might not have all the events allocated
+ * yet, we need to free only allocated ones ...
+ */
+ list_del(&oe->buffer->list);
+ ordered_events_buffer__free(oe->buffer, oe->buffer_idx, oe);
+
+ /* ... and continue with the rest */
+ list_for_each_entry_safe(buffer, tmp, &oe->to_free, list) {
+ list_del(&buffer->list);
+ ordered_events_buffer__free(buffer, MAX_SAMPLE_BUFFER, oe);
}
}

diff --git a/tools/perf/util/ordered-events.h b/tools/perf/util/ordered-events.h
index 8c7a2948593e..1338d5c345dc 100644
--- a/tools/perf/util/ordered-events.h
+++ b/tools/perf/util/ordered-events.h
@@ -25,23 +25,28 @@ struct ordered_events;
typedef int (*ordered_events__deliver_t)(struct ordered_events *oe,
struct ordered_event *event);

+struct ordered_events_buffer {
+ struct list_head list;
+ struct ordered_event event[0];
+};
+
struct ordered_events {
- u64 last_flush;
- u64 next_flush;
- u64 max_timestamp;
- u64 max_alloc_size;
- u64 cur_alloc_size;
- struct list_head events;
- struct list_head cache;
- struct list_head to_free;
- struct ordered_event *buffer;
- struct ordered_event *last;
- ordered_events__deliver_t deliver;
- int buffer_idx;
- unsigned int nr_events;
- enum oe_flush last_flush_type;
- u32 nr_unordered_events;
- bool copy_on_queue;
+ u64 last_flush;
+ u64 next_flush;
+ u64 max_timestamp;
+ u64 max_alloc_size;
+ u64 cur_alloc_size;
+ struct list_head events;
+ struct list_head cache;
+ struct list_head to_free;
+ struct ordered_events_buffer *buffer;
+ struct ordered_event *last;
+ ordered_events__deliver_t deliver;
+ int buffer_idx;
+ unsigned int nr_events;
+ enum oe_flush last_flush_type;
+ u32 nr_unordered_events;
+ bool copy_on_queue;
};

int ordered_events__queue(struct ordered_events *oe, union perf_event *event,
--
2.17.1
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