Clean-up of the new buffer kva allocation code. Also, there was an
error in the !BOUNCE_BUFFERS case.

Fix a problem with the new buffer_map management code. Additionally,
decrease the size of buffer_map to approx 2/3 of what it used to be
(buffer_map can be smaller now.) The original commit of thes

Fix a problem with the new buffer_map management code. Additionally,
decrease the size of buffer_map to approx 2/3 of what it used to be
(buffer_map can be smaller now.) The original commit of these changes
increased the size of buffer_map to the point where the system would
not boot on large systems -- now large systems with large caches will
have even less problems than before.

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Implement a new totally dynamic (up to MAXPHYS) buffer kva allocation
scheme. Additionally, add the capability for checking for unexpected
kernel page faults. The maximum amount of kva space for bu

Implement a new totally dynamic (up to MAXPHYS) buffer kva allocation
scheme. Additionally, add the capability for checking for unexpected
kernel page faults. The maximum amount of kva space for buffers hasn't
been decreased from where it is, but it will now be possible to do so.

This scheme manages the kva space similar to the buffers themselves. If
there isn't enough kva space because of usage or fragementation, buffers
will be reclaimed until a buffer allocation is successful. This scheme
should be very resistant to fragmentation problems until/if the LFS code
is fixed and uses the bogus buffer locking scheme -- but a 'fixed' LFS
is not likely to use such a scheme.

Now there should be NO problem allocating buffers up to MAXPHYS.

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Potentially fix a problem, whereby MSDOSFS can request buffers
larger than the vfs layer can provide. We now automatically support
32K clusters if MSDOSFS is installed, and panic if a filesystem tri

Potentially fix a problem, whereby MSDOSFS can request buffers
larger than the vfs layer can provide. We now automatically support
32K clusters if MSDOSFS is installed, and panic if a filesystem tries
to allocate a buffer larger than MAXBSIZE.

This commit is a result of some "prodding" by BDE.

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Improve the caching of small files like directories, while not
substantially increasing buffer space. Specifically, we double
the number of buffers, but allocate only half the amount of memory
per b

Improve the caching of small files like directories, while not
substantially increasing buffer space. Specifically, we double
the number of buffers, but allocate only half the amount of memory
per buffer. Note that VDIR files aren't cached unless instantiated
in a buffer. This will significantly improve caching.

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Fix a problem that could cause msync (or many other things) to deadlock.
The heuristic for managment of memory backing the buffer cache was
nice, but didn't work due to some architectural problems.

Fix a problem that could cause msync (or many other things) to deadlock.
The heuristic for managment of memory backing the buffer cache was
nice, but didn't work due to some architectural problems. Simplify
and improve the algorithm.

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Fix 4 problems:
Major: When blocking occurs in allocbuf() for VMIO files,
excess wire counts could accumulate.
Major: Pages are incorrectly accumulated into the physical
buffer for

Fix 4 problems:
Major: When blocking occurs in allocbuf() for VMIO files,
excess wire counts could accumulate.
Major: Pages are incorrectly accumulated into the physical
buffer for clustered reads. This happens when bogus
page is needed.
Minor: When reclaiming buffers, the async flag on the buffer
needs to be zero, or the reclaim is not optimal.
Minor: The age flag should be cleared, if a buffer is wanted.

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Fix an spl window, a page manipulation at interrupt time that was
incorrect, and correct the support for B_ORDERED. The spl window
fix was from Peter Wemm, and his questions led me to find the probl

Fix an spl window, a page manipulation at interrupt time that was
incorrect, and correct the support for B_ORDERED. The spl window
fix was from Peter Wemm, and his questions led me to find the problem with
the interrupt time page manipulation.

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Add needed spl protection, and some minor cleanups in vfs_vmio_release.
Submitted by: Peter Wemm <peter@spinner.dialix.com> and me.

Clean up some more problems with freeing busy or wired pages. The
vfs_bio code was not waiting properly for page state until manipulating
it.

A modification that allows the driver strategy to modify the
B_ASYNC flag broke things pretty bad (freeing buffer already on
queue or other wierd buffer queue errors.) The broken code is
left in com

A modification that allows the driver strategy to modify the
B_ASYNC flag broke things pretty bad (freeing buffer already on
queue or other wierd buffer queue errors.) The broken code is
left in commented out, but this makes the problem go away for
now.

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Addition of page coloring support. Various levels of coloring are afforded.
The default level works with minimal overhead, but one can also enable
full, efficient use of a 512K cache. (Parameters c

Addition of page coloring support. Various levels of coloring are afforded.
The default level works with minimal overhead, but one can also enable
full, efficient use of a 512K cache. (Parameters can be generated
to support arbitrary cache sizes also.)

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Add bowrite.

Bowrite guarantees that buffers queued after a call to bowrite will
be written after the specified buffer (on a particular device).
Bowrite does this either by taking advantage of hardw

Add bowrite.

Bowrite guarantees that buffers queued after a call to bowrite will
be written after the specified buffer (on a particular device).
Bowrite does this either by taking advantage of hardware ordering support
(e.g. tagged queueing on SCSI devices) or resorting to a synchronous write.

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Even though this looks like it, this is not a complex code change.
The interface into the "VMIO" system has changed to be more consistant
and robust. Essentially, it is now no longer necessary to ca

Even though this looks like it, this is not a complex code change.
The interface into the "VMIO" system has changed to be more consistant
and robust. Essentially, it is now no longer necessary to call vn_open
to get merged VM/Buffer cache operation, and exceptional conditions
such as merged operation of VBLK devices is simpler and more correct.

This code corrects a potentially large set of problems including the
problems with ktrace output and loaded systems, file create/deletes,
etc.

Most of the changes to NFS are cosmetic and name changes, eliminating
a layer of subroutine calls. The direct calls to vput/vrele have
been re-instituted for better cross platform compatibility.

Reviewed by: davidg

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Add separate kmalloc classes for BIO buffers and Ktrace info.

Fixed a major bug that caused various pmap related panics, hangs, and reboots.

The i386 pmap module uses a special area of kernel virtual memory for mapping
of page tables pages when it needs to mod

Fixed a major bug that caused various pmap related panics, hangs, and reboots.

The i386 pmap module uses a special area of kernel virtual memory for mapping
of page tables pages when it needs to modify another process's virtual
address space. It's called the 'alternate page table map'. There is only one
of them and it's expected that only one process will be using it at once and
that the operation is atomic.
When the merged VM/buffer cache was implemented over a year ago, it became
necessary to rundown VM pages at I/O completion. The unfortunate and
unforeseen side effect of this is that pmap functions are now called at bio
interrupt time. If there happend to be a process using the alternate page
table map when this I/O completion occurred, it was possible for a different
process's address space to be switched into the alternate page table map -
leaving the current pmap process with the wrong address space mapped when
the interrupt completed. This resulted in BAD things happening like pages
being mapped or removed from the wrong address space, etc.. Since a very
common case of a process modifying another process's address space is during
fork when the kernel stack is inserted, one of the most common manifestations
of this bug was the kernel stack not being mapped properly, resulting in a
silent hang or reboot. This made it VERY difficult to troubleshoot this bug
(I've been trying to figure out the cause of this for >6 months). Fortunately,
the set of conditions that must be true before this problem occurs is
sufficiently rare enough that most people never saw the bug occur. As I/O
rates increase, however, so does the frequency of the crashes. This problem
used to kill wcarchive about every 10 days, but in more recent times when
the traffic exceeded >100GB/day, the machine could barely manage 6 hours of
uptime.
The fix is to make certain that no process has the pages mapped that are
involved in the I/O, before the I/O is started. The pages are made busy, so
no process will be able to map them, either, until the I/O has finished.
This side-steps the issue by still allowing the pmap functions to be called
at interrupt time, but also assuring that the alternate page table map won't
be switched.
Unfortunately, this appears to not be the only cause of this problem. :-(

Reviewed by: dyson

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The Great PC98 Merge.

All new code is "#ifdef PC98"ed so this should make no difference to
PC/AT (and its clones) users.

Ok'd by: core
Submitted by: FreeBSD(98) development team

Keep brelse from freeing busy pages.

Make sure that we don't place a busy or held page onto the PQ_CACHE queue.

This set of commits to the VM system does the following, and contain
contributions or ideas from Stephen McKay <syssgm@devetir.qld.gov.au>,
Alan Cox <alc@cs.rice.edu>, David Greenman <davidg@freebsd.

This set of commits to the VM system does the following, and contain
contributions or ideas from Stephen McKay <syssgm@devetir.qld.gov.au>,
Alan Cox <alc@cs.rice.edu>, David Greenman <davidg@freebsd.org> and me:

More usage of the TAILQ macros. Additional minor fix to queue.h.
Performance enhancements to the pageout daemon.
Addition of a wait in the case that the pageout daemon
has to run immediately.
Slightly modify the pageout algorithm.
Significant revamp of the pmap/fork code:
1) PTE's and UPAGES's are NO LONGER in the process's map.
2) PTE's and UPAGES's reside in their own objects.
3) TOTAL elimination of recursive page table pagefaults.
4) The page directory now resides in the PTE object.
5) Implemented pmap_copy, thereby speeding up fork time.
6) Changed the pv entries so that the head is a pointer
and not an entire entry.
7) Significant cleanup of pmap_protect, and pmap_remove.
8) Removed significant amounts of machine dependent
fork code from vm_glue. Pushed much of that code into
the machine dependent pmap module.
9) Support more completely the reuse of already zeroed
pages (Page table pages and page directories) as being
already zeroed.
Performance and code cleanups in vm_map:
1) Improved and simplified allocation of map entries.
2) Improved vm_map_copy code.
3) Corrected some minor problems in the simplify code.
Implemented splvm (combo of splbio and splimp.) The VM code now
seldom uses splhigh.
Improved the speed of and simplified kmem_malloc.
Minor mod to vm_fault to avoid using pre-zeroed pages in the case
of objects with backing objects along with the already
existant condition of having a vnode. (If there is a backing
object, there will likely be a COW... With a COW, it isn't
necessary to start with a pre-zeroed page.)
Minor reorg of source to perhaps improve locality of ref.

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Another sweep over the pmap/vm macros, this time with more focus on
the usage. I'm not satisfied with the naming, but now at least there is
less bogus stuff around.

Correct handling of dirty pages in I/O buffers. The case where pages
residing in a buffer that had been dirtied by a process was being
handled incorrectly. The pages were mistakenly placed into the

Correct handling of dirty pages in I/O buffers. The case where pages
residing in a buffer that had been dirtied by a process was being
handled incorrectly. The pages were mistakenly placed into the
cache queue. This would likely have the effect of mmaped page modifications
being lost when I/O system calls were being used simultaneously to
the same locations in a file.
Submitted by: davidg

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Fix the buffer queue problem differently. The previous fix could panic
with a buffer not on queue panic.

1) Fix a bug that a buffer is removed from a queue, but the
queue type is not set to QUEUE_NONE. This appears to have
caused a hang bug that has been lurking.
2) Fix bugs that brelse'ing locked bu

1) Fix a bug that a buffer is removed from a queue, but the
queue type is not set to QUEUE_NONE. This appears to have
caused a hang bug that has been lurking.
2) Fix bugs that brelse'ing locked buffers do not "free" them, but the
code assumes so. This can cause hangs when LFS is used.
3) Use malloced memory for directories when applicable. The amount
of malloced memory is seriously limited, but should decrease the
amount of memory used by an average directory to 1/4 - 1/2 previous.
This capability is fully tunable. (Note that there is no config
parameter, and might never be.)
4) Bias slightly the buffer cache usage towards non-VMIO buffers. Since
the data in VMIO buffers is not lost when the buffer is reclaimed, this
will help performance. This is adjustable also.

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Enable VMIO for non-VDIR metadata and block device.