Re: Proposal for Updating CRC32C with AVX-512 Algorithm.

On Mon, Aug 26, 2024 at 06:54:58PM +0000, Amonson, Paul D wrote:
>> And this still shows the ~14% regression in your original post?
> 
> At the small buffer sizes the margin of error or "noise" is larger,
> 7-11%. My average could be just bad luck. It will take me a while to
> re-setup for full data collection runs but I can try it again if you
> like.

IMHO that would be useful to establish the current state of the patch set
from a performance standpoint, especially since you've added code intended
to mitigate the regression.

+#define COMP_CRC32C_SMALL(crc, data, len) \
+    ((crc) = pg_comp_crc32c_sse42((crc), (data), (len)))

My interpretation of Andres's upthread suggestion is that we'd add the
length check within the macro instead of introducing a separate one.  We'd
expect the compiler to optimize out comparisons for small lengths known at
compile time and always call the existing implementation (which may still
involve a function pointer in most cases).

-- 
nathan