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okay deraadt@
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(Look ma, I might have broken the tree)
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kern_ipc_10.c for other compat modules.
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on NetBSD's code, as well as some faked Posix RT extensions by me. This makes
at least simple linuxthreads tests work.
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okay art@, millert@
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Noone will wait for it (because noone is allowed to wait for it).
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cpu_exit no longer frees the vmspace and u-area. This is now handled by a
separate kernel thread "reaper". This is to avoid sleeping locks in the
critical path of cpu_exit where we're not allowed to sleep.
From NetBSD
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This is only needed in accounting and has to be done carefully because
the limit structures are shared between processes.
Found by Denis A. Doroshenko, analysed by Hannah Schroeter.
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in a correct way. Use it in all places where the vnode was changed.
(most of the earlier code was incorrect and had races).
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commit messages:
Scheduler bug fixes and reorganization
* fix the ancient nice(1) bug, where nice +20 processes incorrectly
steal 10 - 20% of the CPU, (or even more depending on load average)
* provide a new schedclock() mechanism at a new clock at schedhz, so high
platform hz values don't cause nice +0 processes to look like they are
niced
* change the algorithm slightly, and reorganize the code a lot
* fix percent-CPU calculation bugs, and eliminate some no-op code
=== nice bug === Correctly divide the scheduler queues between niced and
compute-bound processes. The current nice weight of two (sort of, see
`algorithm change' below) neatly divides the USRPRI queues in half; this
should have been used to clip p_estcpu, instead of UCHAR_MAX. Besides
being the wrong amount, clipping an unsigned char to UCHAR_MAX is a no-op,
and it was done after decay_cpu() which can only _reduce_ the value. It
has to be kept <= NICE_WEIGHT * PRIO_MAX - PPQ or processes can
scheduler-penalize themselves onto the same queue as nice +20 processes.
(Or even a higher one.)
=== New schedclock() mechanism === Some platforms should be cutting down
stathz before hitting the scheduler, since the scheduler algorithm only
works right in the vicinity of 64 Hz. Rather than prescale hz, then scale
back and forth by 4 every time p_estcpu is touched (each occurance an
abstraction violation), use p_estcpu without scaling and require schedhz
to be generated directly at the right frequency. Use a default stathz (well,
actually, profhz) / 4, so nothing changes unless a platform defines schedhz
and a new clock.
[ To do: Define these for alpha, where hz==1024, and nice was totally broke.]
=== Algorithm change === The nice value used to be added to the
exponentially-decayed scheduler history value p_estcpu, in _addition_ to
be incorporated directly (with greater weight) into the priority calculation.
At first glance, it appears to be a pointless increase of 1/8 the nice
effect (pri = p_estcpu/4 + nice*2), but it's actually at least 3x that
because it will ramp up linearly but be decayed only exponentially, thus
converging to an additional .75 nice for a loadaverage of one. I killed
this: it makes the behavior hard to control, almost impossible to analyze,
and the effect (~~nothing at for the first second, then somewhat increased
niceness after three seconds or more, depending on load average) pointless.
=== Other bugs === hz -> profhz in the p_pctcpu = f(p_cpticks) calcuation.
Collect scheduler functionality. Try to put each abstraction in just one
place.
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Original work done in FreeBSD, but this code was ported from NetBSD by
Chuck Cranor.
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way than that the parent wait call will never get the status of this child,
says Rob
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Implement SA_NOCLDWAIT by reparenting kids of processes that have
the appropriate bit set to PID 1, and let PID 1 handle the zombie.
This assumes that PID 1 will wait for its kids (which is true of init).
This also includes some FreeBSD sigaction.2.
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Remove the process from zombproc and its parent's child list before freeing
its resources.
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block, but credentials should be alive until the process is really
dead. from tegge@idt.unit.no; netbsd pr#1767
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