Re: [RFC PATCH bpf-next 1/2] bpf: add bpf_strncmp helper

Hi,

On 11/7/2021 4:32 AM, Alexei Starovoitov wrote:

On Sat, Nov 6, 2021 at 1:07 PM Andrii Nakryiko
[off-list ref] wrote:

snip

quoted

quoted

I was thinking whether the proto could be:
long bpf_strncmp(const char *s1, u32 s1_sz, const char *s2)
but I think your version is better though having const string as 1st arg
is a bit odd in normal C.

Why do you think it's better? This is equivalent to `123 == x` if it
was integer comparison, so it feels like bpf_strncmp(s, sz, "blah") is
indeed more natural. No big deal, just curious what's better about it.

Only that helper implementation has two less register moves.
which makes it 51%/49% win for me.
.

I agree with Andrii that bpf_strncmp(s, sz, "blah") is more nature. I can run
some simple benchmarks to show whether or not the difference matters.

Regards,
Tao.