Revive backed out pmap related changes from Feb 2002. The highlights are:

- It actually works this time, honest!
- Fine grained TLB shootdowns for SMP on i386.  IPI's are very expensive,
  so try and optimize things where possible.
- Introduce ranged shootdowns that can be done as a single IPI.
- PG_G support for i386
- Specific-cpu targeted shootdowns.  For example, there is no sense in
  globally purging the TLB cache for where we are stealing a page from
  the local unshared process on the local cpu.  Use pm_active to track
  this.
- Add some instrumentation for the tlb shootdown code.
- Rip out SMP code from <machine/cpufunc.h>
- Try and fix some very bogus PG_G and PG_PS interactions that were bad
  enough to cause vm86 bios calls to break.  vm86 depended on our existing
  bugs and this was the cause of the VESA panics last time.
- Fix the silly one-line error that caused the 'panic: bad pte' last time.
- Fix a couple of other silly one-line errors that should have caused more
  pain than they did.

Some more work is needed:
- pmap_{zero,copy}_page[_idle].  These can be done without IPI's if we
  have a hook in cpu_switch.
- The IPI handlers need some cleanup.  I have a bogus %ds load that can
  be avoided.
- APTD handling is rather bogus and appears to be a large source of
  global TLB IPI shootdowns for no really good reason.

I see speedups of between 1.5% and ~4% on buildworlds in a while 1 loop.
I expect to see a bigger difference when there is significant pageout
activity or the system otherwise has memory shortages.

I have backed out a few optimizations that I had been using over the last
few days in order to be a little more conservative.  I'll revisit these
again over the next few days as the dust settles.

New option:  DISABLE_PG_G - In case I missed something.

1 files changed, 3 insertions, 0 deletions

diff --git a/sys/kern/subr_witness.c b/sys/kern/subr_witness.c
index 73934cb2e3a7..444b087a2880 100644
--- a/sys/kern/subr_witness.c
+++ b/sys/kern/subr_witness.c
@@ -223,6 +223,9 @@ static struct witness_order_list_entry order_lists[] = {
 	{ "icu", &lock_class_mtx_spin },
 #ifdef SMP
 	{ "smp rendezvous", &lock_class_mtx_spin },
+#if defined(__i386__) && defined(APIC_IO)
+	{ "tlb", &lock_class_mtx_spin },
+#endif
 #endif
 	{ "clk", &lock_class_mtx_spin },
 	{ "mutex profiling lock", &lock_class_mtx_spin },