[PATCH] bpf: Avoid allocing memory on memoryless numa node

[PATCH] bpf: Avoid allocing memory on memoryless numa node

[Xianting Tian]

In architecture like powerpc, we can have cpus without any local memory
attached to it. In such cases the node does not have real memory.

Use local_memory_node(), which is guaranteed to have memory.
local_memory_node is a noop in other architectures that does not support
memoryless nodes.

Signed-off-by: Xianting Tian <tian.xianting@h3c.com>
---
 kernel/bpf/cpumap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/cpumap.c b/kernel/bpf/cpumap.c
index 6386b7bb9..2c885c00a 100644
--- a/kernel/bpf/cpumap.c
+++ b/kernel/bpf/cpumap.c
@@ -423,7 +423,7 @@ __cpu_map_entry_alloc(struct bpf_cpumap_val *value, u32 cpu, int map_id)
 	struct xdp_bulk_queue *bq;
 
 	/* Have map->numa_node, but choose node of redirect target CPU */
-	numa = cpu_to_node(cpu);
+	numa = local_memory_node(cpu_to_node(cpu));
 
 	rcpu = kzalloc_node(sizeof(*rcpu), gfp, numa);
 	if (!rcpu)
-- 
2.17.1

Re: [PATCH] bpf: Avoid allocing memory on memoryless numa node

[Alexei Starovoitov]

On Sat, Oct 10, 2020 at 1:55 AM Xianting Tian <tian.xianting@h3c.com> wrote:
>
> In architecture like powerpc, we can have cpus without any local memory
> attached to it. In such cases the node does not have real memory.
>
> Use local_memory_node(), which is guaranteed to have memory.
> local_memory_node is a noop in other architectures that does not support
> memoryless nodes.
...
>         /* Have map->numa_node, but choose node of redirect target CPU */
> -       numa = cpu_to_node(cpu);
> +       numa = local_memory_node(cpu_to_node(cpu));

There are so many calls to cpu_to_node() throughout the kernel.
Are you going to convert all of them one patch at a time to the above sequence?
Why not do this CONFIG_HAVE_MEMORYLESS_NODES
in cpu_to_node() instead?
and save the churn.

RE: [PATCH] bpf: Avoid allocing memory on memoryless numa node

[Tianxianting]

Thanks Alexei for your suggestion,
I will try to do it.

-----Original Message-----
From: Alexei Starovoitov [mailto:alexei.starovoitov@gmail.com] 
Sent: Monday, October 12, 2020 9:21 AM
To: tianxianting (RD) <tian.xianting@h3c.com>
Cc: Alexei Starovoitov <ast@kernel.org>; Daniel Borkmann <daniel@iogearbox.net>; David S. Miller <davem@davemloft.net>; Jakub Kicinski <kuba@kernel.org>; Jesper Dangaard Brouer <hawk@kernel.org>; John Fastabend <john.fastabend@gmail.com>; Martin KaFai Lau <kafai@fb.com>; Song Liu <songliubraving@fb.com>; Yonghong Song <yhs@fb.com>; Andrii Nakryiko <andriin@fb.com>; KP Singh <kpsingh@chromium.org>; Network Development <netdev@vger.kernel.org>; bpf <bpf@vger.kernel.org>; LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] bpf: Avoid allocing memory on memoryless numa node

On Sat, Oct 10, 2020 at 1:55 AM Xianting Tian <tian.xianting@h3c.com> wrote:
>
> In architecture like powerpc, we can have cpus without any local 
> memory attached to it. In such cases the node does not have real memory.
>
> Use local_memory_node(), which is guaranteed to have memory.
> local_memory_node is a noop in other architectures that does not 
> support memoryless nodes.
...
>         /* Have map->numa_node, but choose node of redirect target CPU */
> -       numa = cpu_to_node(cpu);
> +       numa = local_memory_node(cpu_to_node(cpu));

There are so many calls to cpu_to_node() throughout the kernel.
Are you going to convert all of them one patch at a time to the above sequence?
Why not do this CONFIG_HAVE_MEMORYLESS_NODES in cpu_to_node() instead?
and save the churn.