Refresh thread stats info only if asked

[sigsegved]

Looks like the linux process refresh mechanism by default parses all stat files in /proc/<pid>/task/<tid>/stat. This can be expensive for highly threaded applications like nginx which could be using 100s of threads for async io. In most places a user might just be interested in the overall process information without requiring to know all the thread/task stat.

Would it be possible to have a new RefreshKind that supports refreshing only the pid stat?

[GuillaumeGomez]

Definitely sounds like a good idea.

[sigsegved]

Since i know nothing about windows side of things how would you support the same for Windows?

[sigsegved]

Side Note:
I also noticed that we skip processing /proc/<pid>/task/<pid>/stat to avoid double processing but in fact these two stat files will contain different data.

So /proc/<pid>/stat will contains stats like "cpu time" by the whole process but /proc/<pid>/task/<pid>/stat file will contain only the main thread's stat.

So for example: if the process is consuming 1000 clock ticks, and there are 10 threads each consuming 50 clock ticks, then you will see the the main thread will have the rest of the 500 clock ticks. by parsing just the main thread you can easily find the split of cpu usage between main thread and the rest.

[GuillaumeGomez]

So seems like it's still needed.

[sigsegved]

@GuillaumeGomez Any thoughts on

Since i know nothing about windows side of things how would you support the same for Windows?

[GuillaumeGomez]

It's a linux-only feature, so basically this "refresh kind" would do nothing on other platforms.

[sigsegved]

master...sigsegved:sysinfo:master i started working on this but want to check with you if this is going in the right direction.

[GuillaumeGomez]

Seems good to me, but just so you know: it means a lot of processes will not be listed anymore.

[sigsegved]

why would that be the case? I thought all "processes" should still be there, but their "tasks" will be none. Right?