Hi,
On Fri, Nov 15, 2024 at 09:54:33AM -0300, Ranier Vilela wrote:
> There is a tiny typo with V13.
> + /* "len" in the [sizeof(size_t) * 8, inf] range */
I think "[sizeof(size_t) * 8, inf[ range" is correct. Infinity can not be
included
into a interval.
Thinking about it, actually, "[sizeof(size_t) * 8, inf)" (note the ')' at the
end)
might be the proper notation from a mathematical point of view.
> But, I'm not sure if I'm still doing something wrong.
> If so, forgive me for the noise.
>
> Of course I expected "not is_allzeros".
That's the test case which is "wrong" (not the function):
"
size_t pagebytes[BLCKSZ] = {0};
volatile bool result;
pagebytes[BLCKSZ-2] = 1;
result = pg_memory_is_all_zeros_v12(pagebytes, BLCKSZ);
"
The pagebytes is an array of size_t (8 bytes each), so the actual array size
is 8192 * 8 = 65536 bytes.
So, pagebytes[BLCKSZ-2] = 1, sets byte 65528 ((8192-2)*8) to 1.
But the function is checking up to BLCKSZ bytes (8192), so the results you
observed (which are correct).
> Anyway, I made another attempt to optimize a bit more, I don't know if it's
> safe though.
There is an issue in your v14, it calls:
"
return pg_memory_is_all_zeros_simd(ptr, ptr + len);
"
but you defined it that way:
"
static inline bool
pg_memory_is_all_zeros_simd(const size_t *p, const size_t * end)
"
while that should be:
"
static inline bool
pg_memory_is_all_zeros_simd(const void *p, const void *end)
"
Doing so, I do not observe any improvments with v14.
Regards,
--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
