Contributed by: Thomaswuerfl@gmx.de
- In sched_prio(), adjust the run queue for threads which may need to move
to the current queue due to priority propagation .
- In sched_switch(), fix style bug introduced when the KSE support went in.
Columns are 80 chars wide, not 90.
- In sched_switch(), Fix the comparison in the idle case and explicitly
re-initialize the runq in the not propagated case.
- Remove dead code in sched_clock().
- In sched_clock(), If we're an IDLE class td set NEEDRESCHED so that threads
that have become runnable will get a chance to.
- In sched_runnable(), if we're not the IDLETD, we should not consider
curthread when examining the load. This mimics the 4BSD behavior of
returning 0 when the only runnable thread is running.
- In sched_userret(), remove the code for setting NEEDRESCHED entirely.
This is not necessary and is not implemented in 4BSD.
- Use the correct comparison in sched_add() when checking to see if an idle
prio task has had it's priority temporarily elevated.
rounding errors. This was the source of the majority of the
interactivity problems. Reintroduce the old algorithm and its XXX.
- Up the interactivity threshold to 30. It really could stand to be even
a tiny bit higher.
- Let the sleep and run time accumulate up to 5 seconds of history rather
than two. This helps stop XFree86 from becoming non-interactive during
bursts of activity.
elevated either due to priority propagation or because we're in the
kernel in either case, put us on the current queue so that we dont
stop others from using important resources. At some point the priority
elevations from sleeping in the kernel should go away.
- Remove an optimization in sched_userret(). Before we would only set
NEEDRESCHED if there was something of a higher priority available. This
is a trivial optimization and it breaks priority propagation because it
doesn't take threads which we may be blocking into account. Notice that
the thread which is blocking others gets up to one tick of cpu time before
we honor this NEEDRESCHED in sched_clock().
you on the current queue. In the future, it would be nice if priority
propagation could deterministicly pluck a thread off of the next queue
and put it on the current queue. Until then this hack stops us from
holding up our entire current queue, including interrupt handlers, while
a thread on the next queue is blocked while holding Giant.
- Inherit our pctcpu information from our parent.
- Associate logical CPUs on the same physical core with the same kseq.
- Adjust code that assumed there would only be one running thread in any
kseq.
- Wrap the HTT code with a ULE_HTT_EXPERIMENTAL ifdef. This is a start
towards HyperThreading support but it isn't quite there yet.
nice distribution without significantly impacting interactive response.
As a side effect it should also allow batch processes to run for a
slightly longer period which will positively impact their performance.
causing poor interactive performance while unnice processes were running.
The new scheme still allows nice to have an effect on priority but it is
not as dramatic as the effect of the interactivity score.
because the run time exceeds the largest value a signed int can hold.
The real solution involves calculating how far we are over the limit.
To quickly solve this problem we loop removing 1/5th of the current value
until it falls below the limit. The common case requires no passes.
and run time.
- Scale the sleep and run time back via sched_interact_update() in more
places. This is to keep the statistic more accurate.
- Charge a parent one tick for forking a child.
- Add only the run time and not the sleep time to the parents kg when a
thread exits. This allows us to give a penalty for having an expensive
thread exit but does not give a bonus for having an interactive thread
exit.
- Change the SLP_RUN_THROTTLE to limit us to 4/5th and not 1/2.
- Change the SLP_RUN_MAX to two seconds. This keeps bursty interactive
applications like mozilla and openoffice in the interactive range even
through expensive tasks.
- Recalculate the slice after every sleep. This ensures that once a task
has been marked interactive it only has a slice of 1 at the risk of
giving tasks that sleep for a very brief period a longer time slice.
which meant no process would run for longer than 20ms.
- Slightly redo the interactivity scorer. It follows the same algorithm but
in a slightly more correct way. Previously values above half were
incorrect.
- Lower the interactivity threshold to 20. It seems that in testing non-
interactive tasks are hardly ever near there and expensive interactive
tasks can sometimes surpass it. This area needs more testing.
- Remove an unnecessary KTR.
- Fix a case where an idle thread that had an elevated priority due to
priority prop. would be placed back on the idle queue.
- Delay setting NEEDRESCHED until userret() for threads that haad their
priority elevated while in kernel. This gives us the same context switch
optimization as SCHED_4BSD.
- Limit the child's slice to 1 in sched_fork_kse() so we detect its behavior
more quickly.
- Inhert some of the run/slp time from the child in sched_exit_ksegrp().
- Redo some of the priority comparisons so they are more clear.
- Throttle the frequency of sched_pctcpu_update() so that rounding errors
do not make it invalid.
second and equalizing the load between the two most imbalanced CPU. This
is intended to clear up long term load imbalances that would not be handled
by the 'pull' method in sched_choose().
- Pull out some bits of sched_choose() into a kseq_move() function that moves
an arbitrary thread from one kseq to another.
adding it to the nice tables. Therefore, in kseq_add_nice, we should
keep in mind that the load will be 1 if we are the only thread, and not
0.
- Assert that the sched lock is held in all the appropriate places.
- Increase the scope of the sched lock in sched_pctcpu_update().
- Hold the sched lock in sched_runnable(). It is not held by the caller.
- For the 4BSD scheduler, this means that all callers of the static
function resetpriority() now always hold sched_lock, so don't lock
sched_lock explicitly in that function.
since they are going on the current cpu and not their previously assigned
cpu.
- sched_runnable() should only return true in the SMP case if the other
processor has more than one thread that is runnable. We can not steal
curthread.
- Change kseq_print() to accept the cpuid instead of a kseq pointer. This
makes use of this function in ddb much easier.
the current queue if its priority is really elevated. This needs more work
as there are cases where a next queue kse could be holding up what would
be a curr queue kse, and thus hurting interactivity. Also, when a thread
with an elevated priority has its priority lowered it should be placed
back on the next queue.
the second kseq's run queue so that it is referenced by the kse when
it is switched out.
- Spell ksq_rslices properly.
Reported by: Ian Freislich <ianf@za.uu.net>
- Allow user adjustable min and max time slices (suggested by hiten).
- Change the SLP_RUN_MAX to 100ms from 2 seconds so that we learn whether a
process is interactive or not much more quickly.
- Place a process on the current run queue if it is interactive or if it is
running at an interrupt thread priority due to priority prop.
- Use the 'current' timeshare queue for interrupt threads, realtime threads,
and idle threads that are running at higher priority due to priority prop.
This fixes problems where priorities would have been elevated but we would
not check the timeshare run queue until other lower priority tasks were
no longer runnable.
- Keep an array of loads indexed by the priority class as well as a global
load.
- Keep an bucket of nice values with a count of the number of kses currently
runnable with that nice value.
- Keep track of the minimum nice value of any running thread.
- Remove the unused short term sleep accounting. I was attempting to use
this for load balancing but it didn't work out.
- Define a kseq_print() for use with debugging.
- Add KTR debugging at useful places so we can easily debug slice and
priority assignment.
- Decouple the runq assignment from the kseq assignment. kseq_add now keeps
track of statistics. This is done so that the nice and load is still
tracked for the currently running process. Previously if a niced process
was added while a non nice process was running the niced process would
still get a slice since it was not aware of the unnice process.
- Make adjustments for the sched api changes.
- Treat each class specially in kseq_{choose,add,rem}. Let the rest of the
code be less aware of scheduling classes.
- Skip the interactivity calculation for non TIMESHARE ksegrps.
- Move slice and runq selection into kseq_add(). Uninline it now that it's
big.
