On Thu, May 02, 2024 at 05:31:00PM -0400, Steven Rostedt wrote:
> On Wed, 1 May 2024 20:31:06 -0700
> "Paul E. McKenney" <paul...@kernel.org> wrote:
>
> > On Thu, May 02, 2024 at 11:05:01AM +0900, Masami Hiramatsu wrote:
> > > On Wed, 1 May 2024 16:12:37 -0700
> > > "Paul E. McKenney" <paul...@kernel.org> wrote:
> > >
> > > > Note that the immediate pressure for this patch should be relieved by
> > > > the
> > > > NAPI patch series [1], but this sort of problem could easily arise
> > > > again.
> > > >
> > > > When running heavy test workloads with KASAN enabled, RCU Tasks grace
> > > > periods can extend for many tens of seconds, significantly slowing
> > > > trace registration. Therefore, make the registration-side RCU Tasks
> > > > grace period be asynchronous via call_rcu_tasks().
> > >
> > > Good catch! AFAICS, there is no reason to wait for synchronization
> > > when adding a new direct trampoline.
> > > This looks good to me.
> > >
> > > Reviewed-by: Masami Hiramatsu (Google) <mhira...@kernel.org>
> >
> > Thank you very much! I will apply this on my next rebase.
>
> I can take it.
>
> It's not a bug fix but just an performance improvement, so it can go into
> the next merge window.
Very good, and thank you!
I will drop it from RCU as soon as it shows up in either -next or in
mainline.
Thanx, Paul
> -- Steve
>
>
>
> >
> > > Thank you,
> > >
> > > > [1]
> > > > https://lore.kernel.org/all/cover.1710877680.git....@cloudflare.com/
> > > >
> > > > Reported-by: Jakub Kicinski <k...@kernel.org>
> > > > Reported-by: Alexei Starovoitov <a...@kernel.org>
> > > > Reported-by: Chris Mason <c...@fb.com>
> > > > Signed-off-by: Paul E. McKenney <paul...@kernel.org>
> > > > Cc: Steven Rostedt <rost...@goodmis.org>
> > > > Cc: Masami Hiramatsu <mhira...@kernel.org>
> > > > Cc: Mark Rutland <mark.rutl...@arm.com>
> > > > Cc: Mathieu Desnoyers <mathieu.desnoy...@efficios.com>
> > > > Cc: <linux-trace-ker...@vger.kernel.org>
> > > >
> > > > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> > > > index 6c96b30f3d63b..32ea92934268c 100644
> > > > --- a/kernel/trace/ftrace.c
> > > > +++ b/kernel/trace/ftrace.c
> > > > @@ -5365,6 +5365,13 @@ static void
> > > > remove_direct_functions_hash(struct ftrace_hash *hash, unsigned long }
> > > > }
> > > >
> > > > +static void register_ftrace_direct_cb(struct rcu_head *rhp)
> > > > +{
> > > > + struct ftrace_hash *fhp = container_of(rhp, struct
> > > > ftrace_hash, rcu); +
> > > > + free_ftrace_hash(fhp);
> > > > +}
> > > > +
> > > > /**
> > > > * register_ftrace_direct - Call a custom trampoline directly
> > > > * for multiple functions registered in @ops
> > > > @@ -5463,10 +5470,8 @@ int register_ftrace_direct(struct ftrace_ops
> > > > *ops, unsigned long addr) out_unlock:
> > > > mutex_unlock(&direct_mutex);
> > > >
> > > > - if (free_hash && free_hash != EMPTY_HASH) {
> > > > - synchronize_rcu_tasks();
> > > > - free_ftrace_hash(free_hash);
> > > > - }
> > > > + if (free_hash && free_hash != EMPTY_HASH)
> > > > + call_rcu_tasks(&free_hash->rcu,
> > > > register_ftrace_direct_cb);
> > > > if (new_hash)
> > > > free_ftrace_hash(new_hash);
> > >
> > >
> > > --
> > > Masami Hiramatsu (Google) <mhira...@kernel.org>
>
