23.01.2025 11:46, Japin Li пишет:
On Wed, 22 Jan 2025 at 22:44, Japin Li <japi...@hotmail.com> wrote:
On Wed, 22 Jan 2025 at 17:02, Yura Sokolov <y.soko...@postgrespro.ru> wrote:
I believe, I know why it happens: I was in hurry making v2 by
cherry-picking internal version. I reverted some changes in
CalcCuckooPositions manually and forgot to add modulo
PREV_LINKS_HASH_CAPA.
Here's the fix:
pos->pos[0] = hash % PREV_LINKS_HASH_CAPA;
- pos->pos[1] = pos->pos[0] + 1;
+ pos->pos[1] = (pos->pos[0] + 1) % PREV_LINKS_HASH_CAPA;
pos->pos[2] = (hash >> 16) % PREV_LINKS_HASH_CAPA;
- pos->pos[3] = pos->pos[2] + 2;
+ pos->pos[3] = (pos->pos[2] + 2) % PREV_LINKS_HASH_CAPA;
Any way, here's v3:
- excess file "v0-0001-Increase..." removed. I believe it was source
of white-space apply warnings.
- this mistake fixed
- more clear slots strategies + "8 positions in two cache-lines" strategy.
You may play with switching PREV_LINKS_HASH_STRATEGY to 2 or 3 and see
if it affects measurably.
Thanks for your quick fixing. I will retest it tomorrow.
Hi, Yura Sokolov
Here is my test result of the v3 patch:
| case | min | avg | max |
|-------------------------------+------------+------------+------------|
| master (44b61efb79) | 865,743.55 | 871,237.40 | 874,492.59 |
| v3 | 857,020.58 | 860,180.11 | 864,355.00 |
| v3 PREV_LINKS_HASH_STRATEGY=2 | 853,187.41 | 855,796.36 | 858,436.44 |
| v3 PREV_LINKS_HASH_STRATEGY=3 | 863,131.97 | 864,272.91 | 865,396.42 |
It seems there are some performance decreases :( or something I missed?
Hi, Japin.
(Excuse me for duplicating message, I found I sent it only to you first
time).
v3 (as well as v2) doesn't increase NUM_XLOGINSERT_LOCKS itself.
With only 8 in-progress inserters spin-lock is certainly better than any
more complex solution.
You need to compare "master" vs "master + NUM_XLOGINSERT_LOCKS=64" vs
"master + NUM_XLOGINSERT_LOCKS=64 + v3".
And even this way I don't claim "Lock-free reservation" gives any profit.
That is why your benchmarking is very valuable! It could answer, does we
need such not-small patch, or there is no real problem at all?
----
regards
Yura Sokolov aka funny-falcon
