service-config-manager performance issue

[Jiaqing Zhao]

On 2022-02-22 04:00, Joseph Reynolds wrote:
> On 2/21/22 6:41 AM, Jiaqing Zhao wrote:
>> Hi, all
>>
>> When updating service status with service-config-manager, it always takes ~15s for the new status to be applied, which is much longer than it should be.
>>
>> By inspecting the code, I found there is a 15s wait before updating service status in ServiceConfig::startServiceRestartTimer(). (https://github.com/openbmc/service-config-manager/blob/f2744893b77b9dd8903bb13113f4c3ef62c18f04/src/srvcfg_manager.cpp#L382)
>>
>> The 15s-wait is added at first in commit 0084047 (https://github.com/openbmc/service-config-manager/commit/0084047d008fd0ac36f09a232f67ff2fc5314b53).
> 
> Here at IBM we are seeing the same thing.  It looks like that code (https://github.com/openbmc/service-config-manager/blob/master/src/srvcfg_manager.cpp - ServiceConfig::startServiceRestartTimer) was part of the initial commit.  I wonder if the problem is caused by a bug in that code.  (But I am not familiar with the code, and I don't have time to look at it now.)  Is the intention to reload the systemd units but give up after 15 seconds?
> 
> Joseph
>

I think the author intends to execute systemd operations with a 15s timeout. But seems he misused boost::asio::steady_timer. The boost doc (https://www.boost.org/doc/libs/1_78_0/doc/html/boost_asio/reference/steady_timer.html) says the function in async_wait() is called when the timer has expired. So the code in service-config-manager actually calls the apply config function after asynchronously waited for 15s.

I cannot find out the proper a way to set a 15s time limit for the operation. Maybe we can set a max wait rounds of executing a systemd job in systemdUnitAction()? Currently it waits infinitely in ~20ms interval.

Jiaqing

>> I've tested service-config-manager works as expected with the wait removed, and it only takes ~1s for the settings being applied, shall we remove it? And I'd like to ask what is the purpose of this wait to double confirm if removing it will bring any side effect.
>>
>> Thanks,
>> Jiaqing
>