tree d425a47f9b75fb82c41386d356f7c91766ba77d9
parent b910987a7d832e38e9342f0946aeb555a48f9cb0
author Alex Qiu <xqiu@google.com> 1594860981 -0700
committer Willy Tu <wltu@google.com> 1613546000 -0800

sensorcommands: Cache sensor data at 60s interval when requested for SDR

Temporary tuning to mitigate performance issue due to inconsistent dbus
call performance in getSensorMap().

Moving the sensor update time to after finish building the map allow the
data to be cached for the the build time plus sensorMapUpdatePeriod.

A SDR scan is observed to take about half a minute, and SDR is scanned
for 17 times during host boot, which adds minutes to host
boot time. However, sensor reading is seldom invoked during boot, and
the host does not poll for SDR after the first one.
Based on these facts, deploy a trick that turn up cache time to 60
seconds to reduce dbus traffic when SDR is requested, while the sensor
reading update interval is not affected.
No time reduction to `ipmitool sdr` command, because it polls for
both SDR and sensor reading.

Tested:
After issuing host reboot command in BMC, host boot time recorded is
reduced from 14:40 to 11:02.
The fan sensor is still observed to be updated every 2 seconds.

Signed-off-by: Alex Qiu <xqiu@google.com>
Change-Id: If45f5b850854ff5888909636507d1c47840d17b6
Signed-off-by: Willy Tu <wltu@google.com>