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| author | Marcelo Tosatti <mtosatti@redhat.com> | 2012-11-27 23:28:57 -0200 |
|---|---|---|
| committer | Marcelo Tosatti <mtosatti@redhat.com> | 2012-11-27 23:29:11 -0200 |
| commit | 51c19b4f5927f5a646e93d69f73c7e89ea14e737 (patch) | |
| tree | a48486f72dc433fd516684d4441022650429d333 /arch/x86/include/asm/vsyscall.h | |
| parent | 3dc4f7cfb7441e5e0fed3a02fc81cdaabd28300a (diff) | |
| download | linux-0-day-51c19b4f5927f5a646e93d69f73c7e89ea14e737.tar.gz linux-0-day-51c19b4f5927f5a646e93d69f73c7e89ea14e737.tar.xz | |
x86: vdso: pvclock gettime support
Improve performance of time system calls when using Linux pvclock,
by reading time info from fixmap visible copy of pvclock data.
Originally from Jeremy Fitzhardinge.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Diffstat (limited to 'arch/x86/include/asm/vsyscall.h')
| -rw-r--r-- | arch/x86/include/asm/vsyscall.h | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/arch/x86/include/asm/vsyscall.h b/arch/x86/include/asm/vsyscall.h index eaea1d31f7530..80f80955cfd8a 100644 --- a/arch/x86/include/asm/vsyscall.h +++ b/arch/x86/include/asm/vsyscall.h @@ -33,6 +33,26 @@ extern void map_vsyscall(void); */ extern bool emulate_vsyscall(struct pt_regs *regs, unsigned long address); +#ifdef CONFIG_X86_64 + +#define VGETCPU_CPU_MASK 0xfff + +static inline unsigned int __getcpu(void) +{ + unsigned int p; + + if (VVAR(vgetcpu_mode) == VGETCPU_RDTSCP) { + /* Load per CPU data from RDTSCP */ + native_read_tscp(&p); + } else { + /* Load per CPU data from GDT */ + asm("lsl %1,%0" : "=r" (p) : "r" (__PER_CPU_SEG)); + } + + return p; +} +#endif /* CONFIG_X86_64 */ + #endif /* __KERNEL__ */ #endif /* _ASM_X86_VSYSCALL_H */ |