Optimization: Use either monotonic or wall-clock to measure command execution time, to regain up to 4% execution time (#10502)

In #7491 (part of redis 6.2), we started using the monotonic timer instead of mstime to measure
command execution time for stats, apparently this meant sampling the clock 3 times per command
rather than two (wince we also need the wall-clock time).
In some cases this causes a significant overhead.

This PR fixes that by avoiding the use of monotonic timer, except for the cases were we know it
should be extremely fast.
This PR also adds a new INFO field called `monotonic_clock` that shows which clock redis is using.

Co-authored-by: Oran Agra <oran@redislabs.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/src/monotonic.c b/src/monotonic.c
index 5bb4f03bf..608fa351c 100644
--- a/src/monotonic.c
+++ b/src/monotonic.c
@@ -168,3 +168,13 @@ const char * monotonicInit() {
 
     return monotonic_info_string;
 }
+
+const char *monotonicInfoString() {
+    return monotonic_info_string;
+}
+
+monotonic_clock_type monotonicGetType() {
+    if (getMonotonicUs == getMonotonicUs_posix)
+        return MONOTONIC_CLOCK_POSIX;
+    return MONOTONIC_CLOCK_HW;
+}