Re: [PATCH v2] bpf: Allocate bpf_event_entry with node info

Jiri Olsa
2024-05-29T08:31:28Z

On Tue, May 28, 2024 at 11:53:11PM -0700, Namhyung Kim wrote:
> It was reported that accessing perf_event map entry caused pretty high
> LLC misses in get_map_perf_counter(). As reading perf_event is allowed
> for the local CPU only, I think we can use the target CPU of the event
> as hint for the allocation like in perf_event_alloc() so that the event
> and the entry can be in the same node at least.

looks good, is there any profile to prove the gain?

jirka

>
> Reported-by: Aleksei Shchekotikhin <alekseis@google.com>
> Reported-by: Nilay Vaish <nilayvaish@google.com>
> Signed-off-by: Namhyung Kim <namhyung@kernel.org>

> ---
> v2) fix build errors
>
> kernel/bpf/arraymap.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
> index feabc0193852..067f7cf27042 100644
> --- a/kernel/bpf/arraymap.c
> +++ b/kernel/bpf/arraymap.c
> @@ -1194,10 +1194,17 @@ static struct bpf_event_entry *bpf_event_entry_gen(struct file *perf_file,
> struct file *map_file)
> {
> struct bpf_event_entry *ee;
> + struct perf_event *event = perf_file->private_data;
> + int node = -1;
>
> - ee = kzalloc(sizeof(*ee), GFP_KERNEL);
> +#ifdef CONFIG_PERF_EVENTS
> + if (event->cpu >= 0)
> + node = cpu_to_node(event->cpu);
> +#endif
> +
> + ee = kzalloc_node(sizeof(*ee), GFP_KERNEL, node);
> if (ee) {
> - ee->event = perf_file->private_data;
> + ee->event = event;
> ee->perf_file = perf_file;
> ee->map_file = map_file;
> }
> --
> 2.45.1.288.g0e0cd299f1-goog
>