[PING][RFC][PATCH] generic hp_timing

[Maria Guseva]

Ping.

Regards,
Maria

>Ping.

>>Hello,

>>The attached patch is a draft implementation of generic timing: via
clock_gettime, vdso or system call, where available and via gettimeofday
function call otherwise.

>>In order to eliminate performance impact in existing usages of
HP_TIMING_NOW  the HP_TIMING_AVAIL is still set to 0. The generic timing is
enabled only in DL_DEBUG_STATISTICS cases where performance is not critical.

>>However I suggest it may be wrong and we can use at least vdso
clock_gettime as real HP_TIMING. And the rest probably shouldn't be even
considered as high-precision timers and should be moved from hp-timing
header to some new one. 

>>The need of generic timing was discussed in "LD_DEBUG option to measure
init time" patch review:
https://sourceware.org/ml/libc-alpha/2015-08/msg00084.html
>>Proposed there new LD_DEBUG option needs HP_TIMING implementation to be
usable on Arm platform in particular.