Hello Kudu Jenkins, Adar Dembo,
I'd like you to reexamine a change. Please visit
http://gerrit.cloudera.org:8080/14172
to look at the new patch set (#3).
Change subject: [gutil] introduce CLOCK_MONOTONIC_RAW
......................................................................
[gutil] introduce CLOCK_MONOTONIC_RAW
This patch adds an accessor method for the CLOCK_MONOTONIC_RAW clock,
named GetMonoTimeMicrosRaw(). This functionality will be used by
follow-up changelists which implement built-in Kudu NTP client
(one of those is https://gerrit.cloudera.org/#/c/7477).
In essence, CLOCK_MONOTONIC_RAW (CLOCK_UPTIME_RAW on Darwin/macOS)
is a better clock source than CLOCK_MONOTONIC for NTP-related
calculations since CLOCK_MONOTONIC_RAW is not subject to adjustments
by adjtime() and the kernel NTP discipline (see [1]).
CLOCK_MONOTONIC_RAW clock is marching forward always at the same rate,
and that's useful when sampling local clock readings to estimate delays
in NTP packet exchange between the client and the servers, especially
when counting in the skew of the local clock into the computations.
On macOS, GetMonoTimeMicrosRaw() behaves exactly as GetMonoTimeMicros()
since both use mach_absolute_time() which isn't affected by clock
adjustments. On newer versions of Darwin (16.0+) and macOS (10.12+),
GetMonoTimeMicrosRaw() produces the same results as
clock_gettime(CLOCK_UPTIME_RAW, ...), see [2].
References:
1. http://man7.org/linux/man-pages/man2/clock_gettime.2.html
2. http://www.manpagez.com/man/3/clock_gettime/
Change-Id: I88c787fe7aee6aa55943cbadfd2be4f43053f6ad
---
M src/kudu/gutil/walltime.h
1 file changed, 28 insertions(+), 8 deletions(-)
git pull ssh://gerrit.cloudera.org:29418/kudu refs/changes/72/14172/3
--
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Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-MessageType: newpatchset
Gerrit-Change-Id: I88c787fe7aee6aa55943cbadfd2be4f43053f6ad
Gerrit-Change-Number: 14172
Gerrit-PatchSet: 3
Gerrit-Owner: Alexey Serbin <[email protected]>
Gerrit-Reviewer: Adar Dembo <[email protected]>
Gerrit-Reviewer: Kudu Jenkins (120)
