Re: SLRU optimization - configurable buffer pool and partitioning the SLRU lock
| От | tender wang |
|---|---|
| Тема | Re: SLRU optimization - configurable buffer pool and partitioning the SLRU lock |
| Дата | |
| Msg-id | CAHewXNmGoGJYiSMxApNtrtHZ-GVQ_QxpOPnOiRnwKRqq3+fQDQ@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: SLRU optimization - configurable buffer pool and partitioning the SLRU lock ("Andrey M. Borodin" <x4mmm@yandex-team.ru>) |
| Ответы |
Re: SLRU optimization - configurable buffer pool and partitioning the SLRU lock
|
| Список | pgsql-hackers |
Andrey M. Borodin <x4mmm@yandex-team.ru> 于2023年12月14日周四 17:35写道：
> On 14 Dec 2023, at 14:28, tender wang <tndrwang@gmail.com> wrote:
>
> Now that AND is more faster, Can we replace the '% SLRU_MAX_BANKLOCKS' operation in SimpleLruGetBankLock() with '& 127'
unsigned int GetBankno1(unsigned int pageno) {
return pageno & 127;
}
unsigned int GetBankno2(unsigned int pageno) {
return pageno % 128;
}
Generates with -O2
GetBankno1(unsigned int):
mov eax, edi
and eax, 127
ret
GetBankno2(unsigned int):
mov eax, edi
and eax, 127
ret
Compiler is smart enough with constants.
Yeah, that's true.
int GetBankno(long pageno) {
unsigned short bank_mask = 128;
int bankno = (pageno & bank_mask) % 128;
return bankno;
}
enable -O2, only one instruction:
xor eax, eax
But if we all use '%', thing changs as below:
int GetBankno(long pageno) {
unsigned short bank_mask = 128;
int bankno = (pageno % bank_mask) % 128;
return bankno;
}
mov rdx, rdi
sar rdx, 63
shr rdx, 57
lea rax, [rdi+rdx]
and eax, 127
sub eax, edx
sar rdx, 63
shr rdx, 57
lea rax, [rdi+rdx]
and eax, 127
sub eax, edx
Best regards, Andrey Borodin.
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