Function `zend_hash_find_bucket` consumes much time in WordPress workload

Description

Dear, maintainers:
I am utilizing PHP-FPM and have profiled performance data for a WordPress workload. Within this benchmark, I've identified certain hotspots. The performance analysis from 'perf' highlights that functions such as zend_hash_find and zend_hash_find_known_hash are consuming a considerable amount of time. Upon investigation, I suspect that the core issue lies within the zend_hash_find_bucket function.

Upon inspecting the assembly code and annotating it, I noticed that certain 'mov' instructions are causing significant delays. To address this, I attempted to optimize the zend_hash_find_bucket function. I experimented with optimizations such as utilizing prefetch instructions and employing struct alignment. However, these optimizations did not seem to have a discernible impact on performance.

Percent│
       │
       │
       │    Disassembly of section .text:
       │
       │    0000000000532ae0 <zend_hash_find>:
       │    zend_hash_find():
  0.84 │      push %r12
  0.04 │      push %rbp
  0.01 │      mov  %rsi,%rbp
  2.52 │      push %rbx
       │    zend_string_hash_val():
  8.01 │      mov  0x8(%rsi),%rax
       │    zend_hash_find():
  0.02 │      mov  %rdi,%rbx
       │    zend_string_hash_val():
  0.12 │      test %rax,%rax
  0.14 │    ↓ je   78
       │    zend_hash_find_bucket():
  5.63 │13:   or   0xc(%rbx),%eax
  0.28 │      mov  0x10(%rbx),%r12
  0.16 │      cltq
 25.03 │      mov  (%r12,%rax,4),%ebx
  1.98 │      cmp  $0xffffffff,%ebx
  0.56 │    ↓ je   a0
  0.85 │      shl  $0x5,%rbx
  0.50 │      add  %r12,%rbx
 15.20 │      cmp  0x18(%rbx),%rbp
 12.97 │    ↓ jne  68
       │    zend_hash_find():
  1.41 │32:   mov  %rbx,%rax
  0.60 │      pop  %rbx
  0.03 │      pop  %rbp
  1.25 │      pop  %r12
  1.83 │    ← ret
       │      nop
       │    zend_hash_find_bucket():
  0.26 │40:   mov  0x18(%rbx),%rdi
  0.04 │      test %rdi,%rdi
       │    ↓ je   53
       │    zend_string_equal_content():
  0.01 │      mov  0x10(%rbp),%rax
  0.01 │      cmp  %rax,0x10(%rdi)
  5.03 │    ↓ je   90
       │    zend_hash_find_bucket():
  1.06 │53:   mov  0xc(%rbx),%ebx
  0.11 │      cmp  $0xffffffff,%ebx
  0.15 │    ↓ je   a0
  0.33 │      shl  $0x5,%rbx
  0.24 │      add  %r12,%rbx
  1.90 │      cmp  0x18(%rbx),%rbp
  2.69 │    ↑ je   32
  2.00 │68:   mov  0x8(%rbp),%rax
  0.24 │      cmp  %rax,0x10(%rbx)

Is this a known performance issue within the PHP community? I'm seeking suggestions or insights on potential avenues for optimization. Your feedback and suggestions would be greatly appreciated.

PHP Version

master

Operating System

No response

首先阅读 zend_hash_find_bucket 以及相关的 zend_hash_find 和 zend_hash_find_known_hash 入口点，然后针对 WordPress 工作负载复现报告中的 perf 性能分析结果。完成的标准是：提出有依据的更改，并在该工作负载中取得可测量的改进，同时保持哈希查找行为不变。