linux-kernel - Re: [PATCH v2] bpf: Allocate bpf_event

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Date: Wed, 29 May 2024 10:31:24 +0200
From: Jiri Olsa <olsajiri@...il.com>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Andrii Nakryiko <andrii@...nel.org>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>,
	Yonghong Song <yonghong.song@...ux.dev>,
	John Fastabend <john.fastabend@...il.com>,
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...gle.com>,
	Hao Luo <haoluo@...gle.com>, LKML <linux-kernel@...r.kernel.org>,
	bpf@...r.kernel.org, Aleksei Shchekotikhin <alekseis@...gle.com>,
	Nilay Vaish <nilayvaish@...gle.com>
Subject: Re: [PATCH v2] bpf: Allocate bpf_event_entry with node info

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@...gle.com>
> Reported-by: Nilay Vaish <nilayvaish@...gle.com>
> Signed-off-by: Namhyung Kim <namhyung@...nel.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
>