PostgreSQL 15 preview - ARM多核适配 性能提升 - Use ISB as a spin-delay instruction on ARM64

作者

digoal

日期

2022-04-08

标签

PostgreSQL , arm , arm64 , 多核 , 性能 , spin

ARM多核适配 性能提升 - Use ISB as a spin-delay instruction on ARM64

https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=a82a5eee314df52f3183cedc0ecbcac7369243b1

Use ISB as a spin-delay instruction on ARM64.  
author  Tom Lane <tgl@sss.pgh.pa.us>      
Wed, 6 Apr 2022 22:57:57 +0000 (18:57 -0400)  
committer   Tom Lane <tgl@sss.pgh.pa.us>      
Wed, 6 Apr 2022 22:58:14 +0000 (18:58 -0400)  
commit  a82a5eee314df52f3183cedc0ecbcac7369243b1  
tree    66b56e90a4483c68930a083534fc1963859464a7    tree  
parent  8ea7963fc741b6f403a544d56ad0ecf78e5237b1    commit | diff  
Use ISB as a spin-delay instruction on ARM64.  
This seems beneficial on high-core-count machines, and not harmful  
on lesser hardware.  However, older ARM32 gear doesn't have this  
instruction, so restrict the patch to ARM64.  
Geoffrey Blake  
Discussion: https://postgr.es/m/78338F29-9D7F-4DC8-BD71-E9674CE71425@amazon.com  

src/include/storage/s_lock.h

+/*  
+ * Using an ISB instruction to delay in spinlock loops appears beneficial on  
+ * high-core-count ARM64 processors.  It seems mostly a wash for smaller gear,  
+ * and ISB doesn't exist at all on pre-v7 ARM chips.  
+ */  
+#if defined(__aarch64__) || defined(__aarch64)  
+  
+#define SPIN_DELAY() spin_delay()  
+  
+static __inline__ void  
+spin_delay(void)  
+{  
+   __asm__ __volatile__(  
+       " isb;              \n");  
+}  
+  
+#endif  /* __aarch64__ || __aarch64 */  

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