[PATCH] macOS: detect cache line size at runtime

[Piotr Sikora via nginx-devel]

# HG changeset patch
# User Piotr Sikora <pi...@aviatrix.com>
# Date 1708977640 0
#      Mon Feb 26 20:00:40 2024 +0000
# Branch patch015
# Node ID f58bc1041ebca635517b919d58b49923bf24f76d
# Parent  570e97dddeeddb79c71587aa8a10150b64404beb
macOS: detect cache line size at runtime.

Notably, Apple Silicon CPUs have 128 byte cache line size,
which is twice the default configured for generic aarch64.

Signed-off-by: Piotr Sikora <pi...@aviatrix.com>

diff -r 570e97dddeed -r f58bc1041ebc src/os/unix/ngx_darwin_init.c
--- a/src/os/unix/ngx_darwin_init.c     Mon Feb 26 20:00:38 2024 +0000
+++ b/src/os/unix/ngx_darwin_init.c     Mon Feb 26 20:00:40 2024 +0000
@@ -11,6 +11,7 @@
 
 char    ngx_darwin_kern_ostype[16];
 char    ngx_darwin_kern_osrelease[128];
+int64_t ngx_darwin_hw_cachelinesize;
 int     ngx_darwin_hw_ncpu;
 int     ngx_darwin_kern_ipc_somaxconn;
 u_long  ngx_darwin_net_inet_tcp_sendspace;
@@ -44,6 +45,10 @@
 
 
 sysctl_t sysctls[] = {
+    { "hw.cachelinesize",
+      &ngx_darwin_hw_cachelinesize,
+      sizeof(ngx_darwin_hw_cachelinesize), 0 },
+
     { "hw.ncpu",
       &ngx_darwin_hw_ncpu,
       sizeof(ngx_darwin_hw_ncpu), 0 },
@@ -155,6 +160,7 @@
         return NGX_ERROR;
     }
 
+    ngx_cacheline_size = ngx_darwin_hw_cachelinesize;
     ngx_ncpu = ngx_darwin_hw_ncpu;
 
     if (ngx_darwin_kern_ipc_somaxconn > 32767) {
diff -r 570e97dddeed -r f58bc1041ebc src/os/unix/ngx_posix_init.c
--- a/src/os/unix/ngx_posix_init.c      Mon Feb 26 20:00:38 2024 +0000
+++ b/src/os/unix/ngx_posix_init.c      Mon Feb 26 20:00:40 2024 +0000
@@ -51,7 +51,10 @@
     }
 
     ngx_pagesize = getpagesize();
-    ngx_cacheline_size = NGX_CPU_CACHE_LINE;
+
+    if (ngx_cacheline_size == 0) {
+        ngx_cacheline_size = NGX_CPU_CACHE_LINE;
+    }
 
     for (n = ngx_pagesize; n >>= 1; ngx_pagesize_shift++) { /* void */ }
 
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