tree aea2d258cc6c3d265b2a3b0172123852f00ba70c
parent 6aa24d4406bf1675f846d418b79b6616e61ae4bd
author Deepak Kodihalli <dkodihal@in.ibm.com> 1520411980 -0600
committer Deepak Kodihalli <dkodihal@in.ibm.com> 1523331145 -0500

performance: setup sysfs read independent of D-Bus

Previously, phosphor-hwmon had a polling loop to read the sysfs - it
would wakeup every second or when a D-Bus event occurs (in which case it
would service D-Bus and then read sysfs). This causes successive D-Bus
calls to slow down, because hwmon would be busy in the loop, reading
sysfs, after servicing D-Bus.

To solve this, schedule the sysfs read independently of the D-Bus event
loop : add a timer handler to an sd event loop, and attach the D-Bus
event loop to the sd event loop.

Tested: An example of how this helped : the 'dcmi sensors' command (to
read 50 temperature sensors) would take more than 60 seconds on
Witherspoon (based off of master 00f02f3). With this patch, the time
taken is about 15 seconds.

Resolves openbmc/openbmc#2985.

Change-Id: I5f512ed11cb6f5f5d2455863ac8e62b5ada16c7a
Signed-off-by: Deepak Kodihalli <dkodihal@in.ibm.com>