sched_cpu() locks an sx lock (allproc_lock) which can sleep if it fails to
acquire the lock, it is not safe to execute this in a callout handler from
softclock().
use it, if we ever did. They have been been VERY poorly maintained for
some time, possibly because they were a NOP. FWIW, This brings our table
formats back closer to the other *BSD's.
cpu could have been bogged down with non-transferable load and still not
migrated a new thread to an idle cpu. This required some benchmarking and
tuning to get right as the comment above it suggests.
- In sched_add(), do the idle check prior to the transfer check so that we
don't try to transfer load from an idle cpu. This fixes panics caused by
IPIs on UP machines running SMP kernels.
Reported/Debugged by: seanc
reassigning their v_ops field to specfs, detaching from the mountpoint, etc.
However, this is not sufficient. If we vclean() the vnode the pages owned
by the vnode are lost, potentially while buffers reference them. Implement
parts of vclean() seperately in vgonechrl() so that the pages and bufs
associated with a device vnode are not destroyed while in use.
- The new sched_balance_groups() function does intra-group balancing while
sched_balance() balances the available groups.
- Pick a random time between 0 ticks and hz * 2 ticks to restart each
balancing process. Each balancer has its own timeout.
- Pick a random place in the list of groups to start the search for lowest
and highest group loads. This prevents us from prefering a group based on
numeric position.
- Use a nasty hack to stop us from preferring cpu 0. The problem is that
softclock always runs on cpu 0, so it always has a little extra load. We
ignore this load in the balancer for now. In the future softclock should
run on a random cpu and these hacks can go away.
cpu are added to a group.
- Don't place a cpu into the kseq_idle bitmask until all cpus in that group
have idled.
- Prefer idle groups over idle group members in the new kseq_transfer()
function. In this way we will prefer to balance load across full cores
rather than add further load a partial core.
- Before a cpu goes idle, check the other group members for threads. Since
SMT cpus may freely share threads, this is cheap.
- SMT cores may be individually pinned and bound to now. This contrasts the
old mechanism where binding or pinning would have allowed a thread to run
on any available cpu.
- Remove some unnecessary logic from sched_switch(). Priority propagation
should be properly taken care of in sched_prio() now.
turnstile_unpend(). A racing thread that does not have TDI_LOCK set may
either be running on another CPU or it may be sitting on a run queue if it
was preempted during the very small window in turnstile_wait() between
unlocking the turnstile chain lock and locking sched_lock.
case of a turnstile having no threads is just one instance of the more
general case where the thread we are examining has been partially awakened
already in that it has been removed from the turnstile's blocked list but
still has TDI_LOCK set. We detect that case by checking to see if the
thread has already had a turnstile reassigned to it.
functions less noisy: We printf if a new function took longer than
the previous record holder, or of the previous record holder took
more than twice as long as the current record.
to have the kernel switch to a new thread, instead of doing it in
userland. It is in fact needed on ia64 where syscall restarts do not
return to userland first. It's completely handled inside the kernel.
As such, any context created by the kernel as part of an upcall and
caused by some syscall needs to be restored by the kernel.
Be sure to shift (long)1 << 33 and higher, not (int)1. Otherwise bad
things happen(TM). This is why beast.freebsd.org paniced with ULE.
Reviewed by: jeff
and the mpo_create_cred() MAC policy entry point to
mpo_copy_cred_label(). This is more consistent with similar entry
points for creation and label copying, as mac_create_cred() was
called from crdup() as opposed to during process creation. For
a number of policies, this removes the requirement for special
handling when copying credential labels, and improves consistency.
Approved by: re (scottl)
Obtained from: TrustedBSD Project
Sponsored by: DARPA, Network Associates Laboratories
1) mp_maxid is a valid FreeBSD CPU ID in the range 0 .. MAXCPU - 1.
2) For all active CPUs in the system, PCPU_GET(cpuid) <= mp_maxid.
Approved by: re (scottl)
Tested on: i386, amd64, alpha
aid other kernel code, especially code which can be in a module such as
the acpi_cpu(4) driver, to work properly with both SMP and UP kernels.
The exported symbols include mp_ncpus, all_cpus, mp_maxid, smp_started, and
the smp_rendezvous() function. This also means that CPU_ABSENT() is now
always implemented the same on all kernels.
Approved by: re (scottl)
