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Before threads were introduced in 1.8, idle_pct used to be a global
variable indicating the overall process idle time. Threads made it
thread-local, meaning that its reporting in the stats made little
sense, though this was not easy to spot. In 2.0, the idle_pct variable
moved to the struct thread_info via commit 81036f273 ("MINOR: time:
move the cpu, mono, and idle time to thread_info"). It made it more
obvious that the idle_pct was per thread, and also allowed to more
accurately measure it. But no more effort was made in that direction.
This patch introduces a new report_idle() function that accurately
averages the per-thread idle time over all running threads (i.e. it
should remain valid even if some threads are paused or stopped), and
makes use of it in the stats / "show info" reports.
Sending traffic over only two connections of an 8-thread process
would previously show this erratic CPU usage pattern:
$ while :; do socat /tmp/sock1 - <<< "show info"|grep ^Idle;sleep 0.1;done
Idle_pct: 30
Idle_pct: 35
Idle_pct: 100
Idle_pct: 100
Idle_pct: 100
Idle_pct: 100
Idle_pct: 100
Idle_pct: 100
Idle_pct: 35
Idle_pct: 33
Idle_pct: 100
Idle_pct: 100
Idle_pct: 100
Idle_pct: 100
Idle_pct: 100
Idle_pct: 100
Now it shows this more accurate measurement:
$ while :; do socat /tmp/sock1 - <<< "show info"|grep ^Idle;sleep 0.1;done
Idle_pct: 83
Idle_pct: 83
Idle_pct: 83
Idle_pct: 83
Idle_pct: 83
Idle_pct: 83
Idle_pct: 83
Idle_pct: 83
Idle_pct: 83
Idle_pct: 83
Idle_pct: 83
Idle_pct: 83
Idle_pct: 83
Idle_pct: 83
Idle_pct: 83
This is not technically a bug but this lack of precision definitely affects
some users who rely on the idle_pct measurement. This should at least be
backported to 2.4, and might be to some older releases depending on users
demand.
The HAProxy documentation has been split into a number of different files for ease of use. Please refer to the following files depending on what you're looking for : - INSTALL for instructions on how to build and install HAProxy - BRANCHES to understand the project's life cycle and what version to use - LICENSE for the project's license - CONTRIBUTING for the process to follow to submit contributions The more detailed documentation is located into the doc/ directory : - doc/intro.txt for a quick introduction on HAProxy - doc/configuration.txt for the configuration's reference manual - doc/lua.txt for the Lua's reference manual - doc/SPOE.txt for how to use the SPOE engine - doc/network-namespaces.txt for how to use network namespaces under Linux - doc/management.txt for the management guide - doc/regression-testing.txt for how to use the regression testing suite - doc/peers.txt for the peers protocol reference - doc/coding-style.txt for how to adopt HAProxy's coding style - doc/internals for developer-specific documentation (not all up to date)