| From: | Nathan Bossart <nathandbossart(at)gmail(dot)com> |
|---|---|
| To: | "Amonson, Paul D" <paul(dot)d(dot)amonson(at)intel(dot)com> |
| Cc: | Bruce Momjian <bruce(at)momjian(dot)us>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, Andres Freund <andres(at)anarazel(dot)de>, "pgsql-hackers(at)lists(dot)postgresql(dot)org" <pgsql-hackers(at)lists(dot)postgresql(dot)org>, "Shankaran, Akash" <akash(dot)shankaran(at)intel(dot)com> |
| Subject: | Re: Proposal for Updating CRC32C with AVX-512 Algorithm. |
| Date: | 2024-08-26 19:08:05 |
| Message-ID: | ZszSlc__-e3MFoOT@nathan |
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| Lists: | pgsql-hackers |
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
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