Hi Arnaldo,
On Mon, Mar 30, 2015 at 11:02:39AM -0300, Arnaldo Carvalho de Melo wrote:
> Em Mon, Mar 30, 2015 at 10:06:35PM +0900, Namhyung Kim escreveu:
> > On Mon, Mar 30, 2015 at 9:56 PM, Jiri Olsa <jo...@redhat.com> wrote:
> > > On Mon, Mar 30, 2015 at 09:48:52PM +0900, Namhyung Kim wrote:
> > >> > @@ -380,10 +381,13 @@ static struct thread
> > >> > *__machine__findnew_thread(struct machine *machine,
> > >> > if (!create)
> > >> > return NULL;
> > >> >
> > >> > - th = thread__new(pid, tid);
> > >> > + th = thread__new(machine, pid, tid);
> > >> > if (th != NULL) {
> > >> > +
> > >> > + pthread_mutex_lock(&machine->threads_lock);
> > >> > rb_link_node(&th->rb_node, parent, p);
> > >> > rb_insert_color(&th->rb_node, &machine->threads);
> > >> > + pthread_mutex_unlock(&machine->threads_lock);
> > >>
> > >> I think you also need to protect the rb tree traversal above.
> > >
> > > yep, I already have another version.. but it blows on another place ;-)
> > >
> > >>
> > >> But this makes every sample processing grabs and releases the lock so
> > >> might cause high overhead. It can be a problem if such processing is
> > >> done parallelly like my multi-thread work. :-/
> > >
> > > yep.. perhaps instead of more locking we need to find a way where
> > > only single thread do the update on hists/threads
> >
> > Agreed.
> >
> > AFAIK the reason we do ref-counting is to cleanup dead/exited thread
> > for live session like perf top. In that case we can somehow mark
> > to-be-deleted thread and kill it in a safe time/place..
>
> Humm, you mean have another list node in struct threads and add threads
> to another dead_threads like list, i.e. one that is _really_ dead as no
> more refcounts point to it, and then amortize the costs of removing it
> from the rb_tree by removing multiple threads instead of just one?
Yes, I really want to avoid any overhead on the fastpath. Instead of
refcnt, how about marking and deleting dead threads by the perf top's
display thread unless it's not a selected one?
Thanks,
Namhyung
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