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authorPaul Mackerras <paulus@samba.org>2008-10-27 23:56:03 +0000
committerPaul Mackerras <paulus@samba.org>2008-11-06 09:49:22 +1100
commit597bc5c00b666fe123abb0af64f6e86f7ab72a90 (patch)
treef6be6e6f07fb1caff3b670a7ac3df74a621ae364 /arch/powerpc/kernel/asm-offsets.c
parentc73049f6aa58ac1d1a9ca8cb2b415ef97240b2d3 (diff)
powerpc: Improve resolution of VDSO clock_gettime
Currently the clock_gettime implementation in the VDSO produces a result with microsecond resolution for the cases that are handled without a system call, i.e. CLOCK_REALTIME and CLOCK_MONOTONIC. The nanoseconds field of the result is obtained by computing a microseconds value and multiplying by 1000. This changes the code in the VDSO to do the computation for clock_gettime with nanosecond resolution. That means that the resolution of the result will ultimately depend on the timebase frequency. Because the timestamp in the VDSO datapage (stamp_xsec, the real time corresponding to the timebase count in tb_orig_stamp) is in units of 2^-20 seconds, it doesn't have sufficient resolution for computing a result with nanosecond resolution. Therefore this adds a copy of xtime to the VDSO datapage and updates it in update_gtod() along with the other time-related fields. Signed-off-by: Paul Mackerras <paulus@samba.org>
Diffstat (limited to 'arch/powerpc/kernel/asm-offsets.c')
-rw-r--r--arch/powerpc/kernel/asm-offsets.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index 75c5dd0138fd..050abfd5c17c 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -306,6 +306,7 @@ int main(void)
DEFINE(CFG_SYSCALL_MAP32, offsetof(struct vdso_data, syscall_map_32));
DEFINE(WTOM_CLOCK_SEC, offsetof(struct vdso_data, wtom_clock_sec));
DEFINE(WTOM_CLOCK_NSEC, offsetof(struct vdso_data, wtom_clock_nsec));
+ DEFINE(STAMP_XTIME, offsetof(struct vdso_data, stamp_xtime));
DEFINE(CFG_ICACHE_BLOCKSZ, offsetof(struct vdso_data, icache_block_size));
DEFINE(CFG_DCACHE_BLOCKSZ, offsetof(struct vdso_data, dcache_block_size));
DEFINE(CFG_ICACHE_LOGBLOCKSZ, offsetof(struct vdso_data, icache_log_block_size));