[PATCH] x86: Add portable getcpu call

For NUMA optimization and some other algorithms it is useful to have a fast to get the current CPU and node numbers in user space. x86-64 added a fast way to do this in a vsyscall. This adds a generic syscall for other architectures to make it a generic portable facility. I expect some of them will also implement it as a faster vsyscall. The cache is an optimization for the x86-64 vsyscall optimization. Since what the syscall returns is an approximation anyways and user space often wants very fast results it can be cached for some time. The norma methods to get this information in user space are relatively slow The vsyscall is in a better position to manage the cache because it has direct access to a fast time stamp (jiffies). For the generic syscall optimization it doesn't help much, but enforce a valid argument to keep programs portable I only added an i386 syscall entry for now. Other architectures can follow as needed. AK: Also added some cleanups from Andrew Morton

Andi Kleen committed 20 years ago

Commit 3cfc3481 parent c08c8205 files · +37 −1Browse files

Showing the changes to include (2 of 5 files). Show all

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2 files

include/asm-i386/unistd.h +2 −1
include/linux/syscalls.h +2 −0

include/asm-i386/unistd.h+2−1

 #define __NR_tee		315
 #define __NR_vmsplice		316
 #define __NR_move_pages		317
+#define __NR_getcpu		318
 #ifdef __KERNEL__
-#define NR_syscalls 318
+#define NR_syscalls 319
 /*
  * user-visible error numbers are in the range -1 - -128: see

include/linux/syscalls.h+2−0

 struct compat_stat;
 struct compat_timeval;
 struct robust_list_head;
+struct getcpu_cache;
 #include <linux/types.h>
 #include <linux/aio_abi.h>
 				    size_t __user *len_ptr);
 asmlinkage long sys_set_robust_list(struct robust_list_head __user *head,
 				    size_t len);
+asmlinkage long sys_getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *cache);
 #endif