On Sun, May 11, 2025 at 06:30:25PM +0200, Andrew Lunn wrote:

On Sat, May 10, 2025 at 05:41:00PM -0700, Eric Biggers wrote:

quoted

Update networking code that computes the CRC32C of packets to just call
crc32c() without unnecessary abstraction layers.  The result is faster
and simpler code.

Hi Eric

Do you have some benchmarks for these changes?

	Andrew

Do you want benchmarks that show that removing the indirect calls makes things
faster?  I think that should be fairly self-evident by now after dealing with
retpoline for years, but I can provide more details if you need them.

Removing the inefficient use of crc32c_combine() makes a massive difference on
fragmented sk_buffs, since crc32c_combine() is so slow (much slower than the CRC
calculation itself).  However, reverting the workaround commit 4c2f24549644
("sctp: linearize early if it's not GSO") is beyond the scope of this patchset,
so for now the sctp stack doesn't actually call skb_crc32c() on fragmented
sk_buffs.  I can provide microbenchmarks of skb_crc32c() on a fragmented sk_buff
directly though, if you don't think it's clear already.

Of course, please also keep in mind the -118 line diffstat.  Even if it wasn't
faster we should just do it this way anyway.

- Eric