On Wed, 1 May 2024 20:31:06 -0700 "Paul E. McKenney" <[email protected]> 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" <[email protected]> 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) <[email protected]> > > 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. -- Steve > > > Thank you, > > > > > [1] > > > https://lore.kernel.org/all/[email protected]/ > > > > > > Reported-by: Jakub Kicinski <[email protected]> > > > Reported-by: Alexei Starovoitov <[email protected]> > > > Reported-by: Chris Mason <[email protected]> > > > Signed-off-by: Paul E. McKenney <[email protected]> > > > Cc: Steven Rostedt <[email protected]> > > > Cc: Masami Hiramatsu <[email protected]> > > > Cc: Mark Rutland <[email protected]> > > > Cc: Mathieu Desnoyers <[email protected]> > > > Cc: <[email protected]> > > > > > > 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) <[email protected]>
