Date: Sat, 25 Jan 2003 15:20:31 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: Jeff Roberson <jroberson@chesapeake.net> Cc: Steve Kargl <sgk@troutmask.apl.washington.edu>, Robert Watson <rwatson@FreeBSD.ORG>, Gary Jennejohn <garyj@jennejohn.org>, <arch@FreeBSD.ORG> Subject: Re: New scheduler Message-ID: <200301252320.h0PNKVoq090077@apollo.backplane.com> References: <20030125171217.D18109-100000@mail.chesapeake.net>
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Jeff, while investigating your patch I found a couple of possible
issues which I think are causing the time problems.
The first problem is sched_choose() appears to be causing a lot
of ping-ponging because the swap is made permanent. i.e. it
swaps cpu queues but then the new queue (belonging to another cpu)
becomes the current queue. For the current choose it doesn't matter,
but for the NEXT time choose is called it does.
The second issue has to do with the way kg_slptime is calculated.
It just doesn't look right to me. I think a better solution is
to add an additional field, kg_runtime, and rather then trying to
decrement kg_slptime you instead increment kg_runtime, then use
the ratio kg_runtime / kg_slptime to calculate the interactivity
of the process. If either kg_runtime or kg_slptime exceed
SCHED_SLP_MAX, simply scale both down (to deal with overflows).
-Matt
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