Re: [PATCH] mips: add vdso support

[Hauke Mehrtens <hauke@hauke-m.de>]

On 01/24/2016 12:29 AM, Rich Felker wrote:
> On Sat, Jan 23, 2016 at 09:31:58PM +0100, Hauke Mehrtens wrote:
>> vdso support is available on mips starting with kernel 4.4, see kernel
>> commit a7f4df4e21 "MIPS: VDSO: Add implementations of gettimeofday()
>> and clock_gettime()" for details.
>>
>> Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
>> ---
>>  arch/mips/syscall_arch.h | 4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/arch/mips/syscall_arch.h b/arch/mips/syscall_arch.h
>> index e74e0ad..39c0ea3 100644
>> --- a/arch/mips/syscall_arch.h
>> +++ b/arch/mips/syscall_arch.h
>> @@ -161,3 +161,7 @@ static inline long __syscall6(long n, long a, long b, long c, long d, long e, lo
>>  	if (n == SYS_fstatat) __stat_fix(c);
>>  	return r2;
>>  }
>> +
>> +#define VDSO_USEFUL
>> +#define VDSO_CGT_SYM "__vdso_clock_gettime"
>> +#define VDSO_CGT_VER "LINUX_2.6"
>> -- 
>> 2.7.0.rc3
> 
> Nice! Have you tested it on some real hardware with vdso support to
> confirm that it's working properly?
> 
> Rich
> 
Hi Rich,

yes I tested this on Lantiq VRX200 (MIPS 34Kc V5.6) hardware.

I called clock_gettime(CLOCK_MONOTONIC, &tp) 1.000.000 times and it was
about 60% faster with this patch.

without vdso:
root@OpenWrt:/# time ./vdso-test
real    0m 0.95s
user    0m 0.24s
sys     0m 0.70s

with vdso:
root@OpenWrt:/# time /usr/bin/vdso-test
real    0m 0.35s
user    0m 0.34s
sys     0m 0.00s

Hauke