On Sat, Sep 14, 2013 at 11:25:40AM -0600, David Ahern wrote:
> On 9/14/13 10:16 AM, Frederic Weisbecker wrote:
> >>@@ -676,7 +682,12 @@ int perf_session_queue_event(struct perf_session *s,
> >>union perf_event *event,
> >>
> >> new->timestamp = timestamp;
> >> new->file_offset = file_offset;
> >>- new->event = event;
> >>+
> >>+ if (s->copy_on_queue) {
> >>+ new->event = malloc(event->header.size);
> >>+ memcpy(new->event, event, event->header.size);
> >>+ } else
> >>+ new->event = event;
>
> ---8<---
>
> >So do you think it should stay optional? This looks like a global problem, I
> >mean
> >the event can be unmapped anytime for any builtin tool mapping it, right?
>
> Yes. I could make it the default behavior; just overhead in doing
> that (malloc/copy for each event).
Are there any tool that don't suffer from this bug somehow? If not then it must
be applied unconditionally.
>
> >
> >Also we already allocate the sample list node (struct sample_queue) from
> >os->sample
> >buffer. ie: we have our own allocator there.
> >
> >Probably we should reuse that and include the copied event space in "struct
> >sample_queue"?
>
>
> Right, that's where I put the malloc and copy - I kept the relevant
> change above. I take it you are thinking of something different but
> I am not following you. You definitely do NOT want to change struct
> sample_queue to include an event - like this:
>
> diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
> index 51f5edf..866944a 100644
> --- a/tools/perf/util/session.c
> +++ b/tools/perf/util/session.c
> @@ -491,7 +491,7 @@ static perf_event__swap_op perf_event__swap_ops[] = {
> struct sample_queue {
> u64 timestamp;
> u64 file_offset;
> - union perf_event *event;
> + union perf_event event;
Right that's roughly what I thought.
> struct list_head list;
> };
>
> size of event is determined by mmap_event (mmap2_event in latest
> code) which is > 4096 because of the filename argument. Including
> the event directly in sample_queue would balloon memory usage
> (learned this the hard way!).
Ah then perhaps we can allocate with the dynamic size of the event?
>
> >
> >Also looking at it now, it seems we have a bug on the existing code:
> >
> >
> > if (!list_empty(sc)) {
> > new = list_entry(sc->next, struct sample_queue, list);
> > list_del(&new->list);
> > } else if (os->sample_buffer) {
> > new = os->sample_buffer + os->sample_buffer_idx;
> > if (++os->sample_buffer_idx == MAX_SAMPLE_BUFFER)
> > os->sample_buffer = NULL;
> > } else {
> > os->sample_buffer = malloc(MAX_SAMPLE_BUFFER * sizeof(*new));
> > if (!os->sample_buffer)
> > return -ENOMEM;
> > list_add(&os->sample_buffer->list, &os->to_free);
> > os->sample_buffer_idx = 2;
> > new = os->sample_buffer + 1;
> > }
> >
> >If we actually run out of buffer rooms, we should realloc right after and not
> >wait for the next entry, otherwise we loose an event:
> >
> > if (!list_empty(sc)) {
> > new = list_entry(sc->next, struct sample_queue, list);
> > list_del(&new->list);
> > } else {
> > if (os->sample_buffer) {
> > new = os->sample_buffer + os->sample_buffer_idx;
> > if (++os->sample_buffer_idx == MAX_SAMPLE_BUFFER)
> > os->sample_buffer = NULL;
> > }
> >
> > if (!os->sample_buffer) {
> > os->sample_buffer = malloc(MAX_SAMPLE_BUFFER *
> > sizeof(*new));
> > if (!os->sample_buffer)
> > return -ENOMEM;
> > list_add(&os->sample_buffer->list, &os->to_free);
> > os->sample_buffer_idx = 2;
> > new = os->sample_buffer + 1;
> > }
> >
> >
> >Although the mirrored os->sample_buffer condition check is a bit ugly and
> >should move to
> >a function. But the idea is there.
>
> Ok. That should be a separate patch. Are you going to submit that one?
Yeah, unless you beat me at it :)
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