lkml.org 
[lkml]   [2018]   [Aug]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCHv2] perf tools: Add struct ordered_events_buffer layer
On Wed, Aug 15, 2018 at 10:48:25AM +0200, Jiri Olsa wrote:
> On Tue, Aug 14, 2018 at 12:14:19AM -0700, Stephane Eranian wrote:
>
> SNIP
>
> > > @@ -104,11 +110,12 @@ static struct ordered_event *alloc_event(struct ordered_events *oe,
> > > 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) {
> > > @@ -122,9 +129,8 @@ 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];
> >
> > Ok, but I think this section between the malloc() and the line above
> > needs some comments to clarify what is going on.
> > It is still hard to read.
>
> ok, I put some bigger comment at the top, but I'm not too happy
> feel free to suggest different one ;-)
>
> >
> > > } else {
> > > pr("allocation limit reached %" PRIu64 "B\n", oe->max_alloc_size);
> > > }
> > > @@ -300,15 +306,27 @@ 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,
> > > + struct ordered_events *oe)
> > > +{
> > > + if (oe->copy_on_queue) {
> > > + unsigned int i;
> > > +
> > > + for (i = 0; i < MAX_SAMPLE_BUFFER; i++)
> > > + __free_dup_event(oe, buffer->event[i].event);
> > > + }
> > > +
> > I have a problem with this one, given that the buffer->event[] is
> > never actually zeroed.
> > So what happens if you do not use all the entries by the time you have to free?
> > I think one way to avoid this is by iterating only all the way to
> > oe->buffer_idx.
>
> right, please check attached patch

any comments? attaching v2

thanks,
jirka


---
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-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 | 82 +++++++++++++++++++++++++++-----
tools/perf/util/ordered-events.h | 37 +++++++-------
2 files changed, 90 insertions(+), 29 deletions(-)

diff --git a/tools/perf/util/ordered-events.c b/tools/perf/util/ordered-events.c
index bad9e0296e9a..3672060508a7 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) {
@@ -122,9 +156,8 @@ 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);
}
@@ -300,15 +333,38 @@ 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
\
 
 \ /
  Last update: 2018-08-27 11:28    [W:0.071 / U:7.268 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site