> On Thu, 9 Mar 2023 14:45:21 +0100
> Uladzislau Rezki <urezki@xxxxxxxxx> wrote:
>
> > > The kvfree_rcu()'s single argument name is deprecated therefore
> > > rename it to kvfree_rcu_mightsleep() variant. The goal is explicitly
> > > underline that it is for sleepable contexts.
> > >
> > > Cc: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
> > > Signed-off-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
> > >
> > Could you please add you reviwed-by or Acked-by tags so we can bring
> > our series with renaming for the next merge window?
>
> I don't know. Perhaps we should just apply this patch and not worry about
> sleeping and whatnot.
>
> -- Steve
>
> diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
> index 04f0fdae19a1..5de945a8f61d 100644
> --- a/kernel/trace/trace_osnoise.c
> +++ b/kernel/trace/trace_osnoise.c
> @@ -76,6 +76,7 @@ static unsigned long osnoise_options = OSN_DEFAULT_OPTIONS;
> struct osnoise_instance {
> struct list_head list;
> struct trace_array *tr;
> + struct rcu_head rcu;
> };
>
> static struct list_head osnoise_instances;
> @@ -159,7 +160,7 @@ static void osnoise_unregister_instance(struct trace_array *tr)
> if (!found)
> return;
>
> - kvfree_rcu(inst);
> + kvfree_rcu(inst, rcu);
> }
>
> /*
> diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
> index 20d0c4a97633..ef5fafb40c76 100644
> --- a/kernel/trace/trace_probe.c
> +++ b/kernel/trace/trace_probe.c
> @@ -1172,7 +1172,7 @@ int trace_probe_remove_file(struct trace_probe *tp,
> return -ENOENT;
>
> list_del_rcu(&link->list);
> - kvfree_rcu(link);
> + kvfree_rcu(link, rcu);
>
> if (list_empty(&tp->event->files))
> trace_probe_clear_flag(tp, TP_FLAG_TRACE);
> diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
> index ef8ed3b65d05..e6037752dcf0 100644
> --- a/kernel/trace/trace_probe.h
> +++ b/kernel/trace/trace_probe.h
> @@ -256,6 +256,7 @@ struct trace_probe {
> struct event_file_link {
> struct trace_event_file *file;
> struct list_head list;
> + struct rcu_head rcu;
> };
>
> static inline bool trace_probe_test_flag(struct trace_probe *tp,
>
struct foo_a {
int a;
int b;
};
your obj size is 8 byte
struct foo_b {
struct rcu_head rcu;
int a;
int b;
};
now it becomes 16 + 8 = 24 bytes. In reallity a foo_b object
will be 32 bytes since there is no slab for 24 bytes:
<snip>
kmalloc-32 19840 19840 32 128 1 : tunables 0 0 0 : slabdata 155 155 0
kmalloc-16 28857 28928 16 256 1 : tunables 0 0 0 : slabdata 113 113 0
kmalloc-8 37376 37376 8 512 1 : tunables 0 0 0 : slabdata 73 73 0
<snip>
if we allocate 512 objects of foo_a it would be 4096 bytes
in case of foo_b it is 24 * 512 = 12228 bytes.
single argument will give you 4096 + 512 * 8 = 8192 bytes
int terms of memory consumtion.
And double argument will not give you better performance comparing
with a single argument.
So it depends on what you want to achieve by that patch.
--
Uladzislau Rezki
