- fix precision
when one convert to seconds and then multiply
we can have precision errors
for example if one have 77ms, it will go to 0 when converted to seconds
and then multiply that 0 by 1000 will return 0 instead of 77ms.
- fix mismatch nsec/usec
nsec was multiplied by 1000*1000 while usec by 1000*1000*1000
it should be the opposite.
anyway the implementation had changed.
- implementation description
* env_ticks_to_msec: j / (tick_hz / 1000)
this is exactly the same as (j * 1000) / tick_hz (eq #2).
but this implementation (eq #2) can only handle 54b in j (before overflowing)
because of the multiplication by 1000 (10b).
with the correct implementation we use all 64b in j.
we assume that tick_hz will be prefectly divisible by 1000 so we are ok.
* env_ticks_to_usec: j / (tick_hz / (1000 * 1000))
same as in msec case, we use all 64b in j.
here we assume that tick_hz is perfectly divisible by (1000 * 1000)
i.e. we assume that CPU frequency is some multiple of 1MHz.
* env_ticks_to_nsec: (j * 1000) / (tick_hz / (1000 * 1000))
in this case we can't assume that tick_hz is divisible by 10^9
because there are many CPUs with 2.8GHz or 3.3GHz for example.
so we multiply j by 1000
this means that we can only handle correctly j up to 54b.
(64b - 10b, 10b for the *1000 operation)
Signed-off-by: Amir Haroush <amir.haroush@huawei.com>
Signed-off-by: Shai Fultheim <shai.fultheim@huawei.com>
Change-Id: Ia8ea7f88b718df206fa0731e3f39f419ee922aa7
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/17078
Community-CI: Mellanox Build Bot
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
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