[haiku-bugs] Re: [Haiku] #10454: New scheduler: substantial performance drop
- From: "pdziepak" <trac@xxxxxxxxxxxx>
- Date: Wed, 26 Feb 2014 23:30:52 -0000
#10454: New scheduler: substantial performance drop
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Reporter: stippi | Owner: pdziepak
Type: task | Status: in-progress
Priority: high | Milestone: R1
Component: System/Kernel | Version: R1/Development
Resolution: | Keywords:
Blocked By: 10487 | Blocking:
Has a Patch: 0 | Platform: All
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Comment (by pdziepak):
I've noticed recently that the scheduler tends to keep one core unoccupied
despite having correct core load statistics. That behaviour is not shown
on the graph Stephan posted, but still, it is apparently some oversight in
thread migration logic.
There is also another potential cause for these performance problems
which, actually, has already worried me for some time, but I never looked
into it more closely. When a core is chosen for a thread (in low latency
mode) the scheduler first considers cores that are currently idle. The
purpose of that is to allow the thread to run immediately. However, core
with 90% is idle for 10% of the time and in worst-case scenario may be
chosen by the scheduler even if there were much less occupied cores. The
fix for that shouldn't be very complicated (testing the impact of that fix
probably would take more time, though), all that needs to be done is not
allow cores with a load above certain threshold in idle core list.
I am going to address these issues in a few days.
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Ticket URL: <https://dev.haiku-os.org/ticket/10454#comment:15>
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