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[RFC][PATCH] generic hp_timing


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.

Regards,
Maria

Attachment: Generic-hp-timing.patch
Description: Binary data


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