Re: [PATCH 5/8] lib/crc: arm: Enable arm64's NEON intrinsics implementation of crc64

[Josh Law]

Hi Ard,

Wow, 20x improvement is nuts.

I like how you handle this change *safely*

Like.

+static inline u64 crc64_nvme_arch(u64 crc, const u8 *p, size_t len)
+{
+	if (len >= 128 && static_branch_likely(&have_pmull) &&
+	    likely(may_use_simd())) {
+		do {
+			size_t chunk = min_t(size_t, len & ~15, SZ_4K);
+
+			scoped_ksimd()
+				crc = crc64_nvme_neon(crc, p, chunk);
+
+			p += chunk;
+			len -= chunk;
+		} while (len >= 128);
+	}

chunking the SIMD work at SZ_4K to avoid hogging the CPU and allowing
softirqs/preemption to process is a great detail. 

It’s easy to just wing it and throw
the entire buffer at the FPU, but respecting the kernel's latency
requirements is better!


Reviewed-by: Josh Law <joshlaw48 at gmail.com>

Thanks!