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From: Eric van Gyzen <eric@vangyzen.net>
Subject: td_swvoltick
To: FreeBSD Current <freebsd-current@FreeBSD.org>
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Date: Fri, 12 Jan 2018 13:31:41 -0600
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should_yield() compares thread::td_swvoltick to 'ticks' to determine
whether a thread is hogging and should yield.  Since td_swvoltick
records 'ticks' /before/ the actual context switch, the calculation in
should_yield() includes any time that the thread was switched out.  It
seems that should_yield() wants to know how long the thread has actually
been running.  Therefore, td_swvoltick should record 'ticks' /after/
sched_switch() returns.

Does this make sense, or am I missing something?

If this makes sense, I would probably keep the current assignment in
mi_switch() and simply add a second assignment after the call to
sched_switch().  That way, db_show_thread will still show useful data
for sleeping threads.  I would do the same for td_swinvolticks.

I'll be happy to make the change myself.  I just want a sanity check
before I bother.

Thanks in advance,

Eric