problems. Tor Egge and others have helped with various VM bugs
lately, but don't blame him -- blame me!!!
pmap.c:
1) Create an object for kernel page table allocations. This
fixes a bogus allocation method previously used for such, by
grabbing pages from the kernel object, using bogus pindexes.
(This was a code cleanup, and perhaps a minor system stability
issue.)
pmap.c:
2) Pre-set the modify and accessed bits when prudent. This will
decrease bus traffic under certain circumstances.
vfs_bio.c, vfs_cluster.c:
3) Rather than calculating the beginning virtual byte offset
multiple times, stick the offset into the buffer header, so
that the calculated offset can be reused. (Long long multiplies
are often expensive, and this is a probably unmeasurable performance
improvement, and code cleanup.)
vfs_bio.c:
4) Handle write recursion more intelligently (but not perfectly) so
that it is less likely to cause a system panic, and is also
much more robust.
vfs_bio.c:
5) getblk incorrectly wrote out blocks that are incorrectly sized.
The problem is fixed, and writes blocks out ONLY when B_DELWRI
is true.
vfs_bio.c:
6) Check that already constituted buffers have fully valid pages. If
not, then make sure that the B_CACHE bit is not set. (This was
a major source of Sig-11 type problems.)
vfs_bio.c:
7) Fix a potential system deadlock due to an incorrectly specified
sleep priority while waiting for a buffer write operation. The
change that I made opens the system up to serious problems, and
we need to examine the issue of process sleep priorities.
vfs_cluster.c, vfs_bio.c:
8) Make clustered reads work more correctly (and more completely)
when buffers are already constituted, but not fully valid.
(This was another system reliability issue.)
vfs_subr.c, ffs_inode.c:
9) Create a vtruncbuf function, which is used by filesystems that
can truncate files. The vinvalbuf forced a file sync type operation,
while vtruncbuf only invalidates the buffers past the new end of file,
and also invalidates the appropriate pages. (This was a system reliabiliy
and performance issue.)
10) Modify FFS to use vtruncbuf.
vm_object.c:
11) Make the object rundown mechanism for OBJT_VNODE type objects work
more correctly. Included in that fix, create pager entries for
the OBJT_DEAD pager type, so that paging requests that might slip
in during race conditions are properly handled. (This was a system
reliability issue.)
vm_page.c:
12) Make some of the page validation routines be a little less picky
about arguments passed to them. Also, support page invalidation
change the object generation count so that we handle generation
counts a little more robustly.
vm_pageout.c:
13) Further reduce pageout daemon activity when the system doesn't
need help from it. There should be no additional performance
decrease even when the pageout daemon is running. (This was
a significant performance issue.)
vnode_pager.c:
14) Teach the vnode pager to handle race conditions during vnode
deallocations.
has been some bitrot and incorrect assumptions in the vfs_bio code. These
problems have manifest themselves worse on NFS type filesystems, but can
still affect local filesystems under certain circumstances. Most of
the problems have involved mmap consistancy, and as a side-effect broke
the vfs.ioopt code. This code might have been committed seperately, but
almost everything is interrelated.
1) Allow (pmap_object_init_pt) prefaulting of buffer-busy pages that
are fully valid.
2) Rather than deactivating erroneously read initial (header) pages in
kern_exec, we now free them.
3) Fix the rundown of non-VMIO buffers that are in an inconsistent
(missing vp) state.
4) Fix the disassociation of pages from buffers in brelse. The previous
code had rotted and was faulty in a couple of important circumstances.
5) Remove a gratuitious buffer wakeup in vfs_vmio_release.
6) Remove a crufty and currently unused cluster mechanism for VBLK
files in vfs_bio_awrite. When the code is functional, I'll add back
a cleaner version.
7) The page busy count wakeups assocated with the buffer cache usage were
incorrectly cleaned up in a previous commit by me. Revert to the
original, correct version, but with a cleaner implementation.
8) The cluster read code now tries to keep data associated with buffers
more aggressively (without breaking the heuristics) when it is presumed
that the read data (buffers) will be soon needed.
9) Change to filesystem lockmgr locks so that they use LK_NOPAUSE. The
delay loop waiting is not useful for filesystem locks, due to the
length of the time intervals.
10) Correct and clean-up spec_getpages.
11) Implement a fully functional nfs_getpages, nfs_putpages.
12) Fix nfs_write so that modifications are coherent with the NFS data on
the server disk (at least as well as NFS seems to allow.)
13) Properly support MS_INVALIDATE on NFS.
14) Properly pass down MS_INVALIDATE to lower levels of the VM code from
vm_map_clean.
15) Better support the notion of pages being busy but valid, so that
fewer in-transit waits occur. (use p->busy more for pageouts instead
of PG_BUSY.) Since the page is fully valid, it is still usable for
reads.
16) It is possible (in error) for cached pages to be busy. Make the
page allocation code handle that case correctly. (It should probably
be a printf or panic, but I want the system to handle coding errors
robustly. I'll probably add a printf.)
17) Correct the design and usage of vm_page_sleep. It didn't handle
consistancy problems very well, so make the design a little less
lofty. After vm_page_sleep, if it ever blocked, it is still important
to relookup the page (if the object generation count changed), and
verify it's status (always.)
18) In vm_pageout.c, vm_pageout_clean had rotted, so clean that up.
19) Push the page busy for writes and VM_PROT_READ into vm_pageout_flush.
20) Fix vm_pager_put_pages and it's descendents to support an int flag
instead of a boolean, so that we can pass down the invalidate bit.
2) Do not unnecessarily force page blocking when paging
pages out.
3) Further improve swap pager performance and correctness,
including fixing the paging in progress deadlock (except
in severe I/O error conditions.)
4) Enable vfs_ioopt=1 as a default.
5) Fix and enable the page prezeroing in SMP mode.
All in all, SMP systems especially should show a significant
improvement in "snappyness."
of the various ad-hoc schemes.
2) When bringing in UPAGES, the pmap code needs to do another vm_page_lookup.
3) When appropriate, set the PG_A or PG_M bits a-priori to both avoid some
processor errata, and to minimize redundant processor updating of page
tables.
4) Modify pmap_protect so that it can only remove permissions (as it
originally supported.) The additional capability is not needed.
5) Streamline read-only to read-write page mappings.
6) For pmap_copy_page, don't enable write mapping for source page.
7) Correct and clean-up pmap_incore.
8) Cluster initial kern_exec pagin.
9) Removal of some minor lint from kern_malloc.
10) Correct some ioopt code.
11) Remove some dead code from the MI swapout routine.
12) Correct vm_object_deallocate (to remove backing_object ref.)
13) Fix dead object handling, that had problems under heavy memory load.
14) Add minor vm_page_lookup improvements.
15) Some pages are not in objects, and make sure that the vm_page.c can
properly support such pages.
16) Add some more page deficit handling.
17) Some minor code readability improvements.
MUST be PG_BUSY. It is bogus to free a page that isn't busy,
because it is in a state of being "unavailable" when being
freed. The additional advantage is that the page_remove code
has a better cross-check that the page should be busy and
unavailable for other use. There were some minor problems
with the collapse code, and this plugs those subtile "holes."
Also, the vfs_bio code wasn't checking correctly for PG_BUSY
pages. I am going to develop a more consistant scheme for
grabbing pages, busy or otherwise. For now, we are stuck
with the current morass.
1) Start using TSM.
Struct procs continue to point to upages structure, after being freed.
Struct vmspace continues to point to pte object and kva space for kstack.
u_map is now superfluous.
2) vm_map's don't need to be reference counted. They always exist either
in the kernel or in a vmspace. The vmspaces are managed by reference
counts.
3) Remove the "wired" vm_map nonsense.
4) No need to keep a cache of kernel stack kva's.
5) Get rid of strange looking ++var, and change to var++.
6) Change more data structures to use our "zone" allocator. Added
struct proc, struct vmspace and struct vnode. This saves a significant
amount of kva space and physical memory. Additionally, this enables
TSM for the zone managed memory.
7) Keep ioopt disabled for now.
8) Remove the now bogus "single use" map concept.
9) Use generation counts or id's for data structures residing in TSM, where
it allows us to avoid unneeded restart overhead during traversals, where
blocking might occur.
10) Account better for memory deficits, so the pageout daemon will be able
to make enough memory available (experimental.)
11) Fix some vnode locking problems. (From Tor, I think.)
12) Add a check in ufs_lookup, to avoid lots of unneeded calls to bcmp.
(experimental.)
13) Significantly shrink, cleanup, and make slightly faster the vm_fault.c
code. Use generation counts, get rid of unneded collpase operations,
and clean up the cluster code.
14) Make vm_zone more suitable for TSM.
This commit is partially as a result of discussions and contributions from
other people, including DG, Tor Egge, PHK, and probably others that I
have forgotten to attribute (so let me know, if I forgot.)
This is not the infamous, final cleanup of the vnode stuff, but a necessary
step. Vnode mgmt should be correct, but things might still change, and
there is still some missing stuff (like ioopt, and physical backing of
non-merged cache files, debugging of layering concepts.)
config option in pmap. Fix a problem with faulting in pages. Clean-up
some loose ends in swap pager memory management.
The system should be much more stable, but all subtile bugs aren't fixed yet.
Fix the UIO optimization code.
Fix an assumption in vm_map_insert regarding allocation of swap pagers.
Fix an spl problem in the collapse handling in vm_object_deallocate.
When pages are freed from vnode objects, and the criteria for putting
the associated vnode onto the free list is reached, either put the
vnode onto the list, or put it onto an interrupt safe version of the
list, for further transfer onto the actual free list.
Some minor syntax changes changing pre-decs, pre-incs to post versions.
Remove a bogus timeout (that I added for debugging) from vn_lock.
PHK will likely still have problems with the vnode list management, and
so do I, but it is better than it was.
of vnodes and objects. There are some metadata performance improvements
that come along with this. There are also a few prototypes added when
the need is noticed. Changes include:
1) Cleaning up vref, vget.
2) Removal of the object cache.
3) Nuke vnode_pager_uncache and friends, because they aren't needed anymore.
4) Correct some missing LK_RETRY's in vn_lock.
5) Correct the page range in the code for msync.
Be gentle, and please give me feedback asap.
the pageout daemon wasn't always being waken up appropriately when the
(cache + free) queues were depleted.
Submitted by: David S. Miller <davem@jenolan.rutgers.edu>
changes, so don't expect to be able to run the kernel as-is (very well)
without the appropriate Lite/2 userland changes.
The system boots and can mount UFS filesystems.
Untested: ext2fs, msdosfs, NFS
Known problems: Incorrect Berkeley ID strings in some files.
Mount_std mounts will not work until the getfsent
library routine is changed.
Reviewed by: various people
Submitted by: Jeffery Hsu <hsu@freebsd.org>
This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.
Boy, I'm glad we're not using sup anymore. This update would have been
insane otherwise.
problem of allocating contiguous buffer memory in general, but
make it much more likely to work at boot-up time. The best
chance for an LKM-type load of a sound driver is immediately
after the mount of the root filesystem.
This appears to work for a 64K allocation on an 8MB system.
`show vmopag', `show page' and `show pageq'. Moved all vm ddb stuff
to the ends of the vm source files.
Changed printf() to db_printf(), `indent' to db_indent, and iprintf()
to db_iprintf() in ddb commands. Moved db_indent and db_iprintf()
from vm to ddb.
vm_page.c:
Don't use __pure. Staticized.
db_output.c:
Reduced page width from 80 to 79 to inhibit double spacing for long
lines (there are still some problems if words are printed across
column 79).
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.)
problem with the 'shell scripts' was found, but there was a 'strange'
problem found with a 486 laptop that we could not find. This commit
backs the code back to 25-jul, and will be re-entered after the snapshot
in smaller (more easily tested) chunks.
performance issues.
1) The pmap module has had too many inlines, and so the
object file is simply bigger than it needs to be.
Some common code is also merged into subroutines.
2) Removal of some *evil* PHYS_TO_VM_PAGE macro calls.
Unfortunately, a few have needed to be added also.
The removal caused the need for more vm_page_lookups.
I added lookup hints to minimize the need for the
page table lookup operations.
3) Removal of some bogus performance improvements, that
mostly made the code more complex (tracking individual
page table page updates unnecessarily). Those improvements
actually hurt 386 processors perf (not that people who
worry about perf use 386 processors anymore :-)).
4) Changed pv queue manipulations/structures to be TAILQ's.
5) The pv queue code has had some performance problems since
day one. Some significant scalability issues are resolved
by threading the pv entries from the pmap AND the physical
address instead of just the physical address. This makes
certain pmap operations run much faster. This does
not affect most micro-benchmarks, but should help loaded system
performance *significantly*. DG helped and came up with most
of the solution for this one.
6) Most if not all pmap bit operations follow the pattern:
pmap_test_bit();
pmap_clear_bit();
That made for twice the necessary pv list traversal. The
pmap interface now supports only pmap_tc_bit type operations:
pmap_[test/clear]_modified, pmap_[test/clear]_referenced.
Additionally, the modified routine now takes a vm_page_t arg
instead of a phys address. This eliminates a PHYS_TO_VM_PAGE
operation.
7) Several rewrites of routines that contain redundant code to
use common routines, so that there is a greater likelihood of
keeping the cache footprint smaller.
Re-enables the RSS limiting, and the routine is now tail-recursive,
making it much more safe (eliminates the possiblity of kernel stack
overflow.) Also, the RSS limiting is a little more intelligent about
finding the likely objects that are pushing the process over the limit.
Added some sysctls that help with VM system tuning.
New sysctl features:
1) Enable/disable lru pageout algorithm.
vm.pageout_algorithm = 0, default algorithm that works
well, especially using X windows and heavy
memory loading. Can have adverse effects,
sometimes slowing down program loading.
vm.pageout_algorithm = 1, close to true LRU. Works much
better than clock, etc. Does not work as well as
the default algorithm in general. Certain memory
"malloc" type benchmarks work a little better with
this setting.
Please give me feedback on the performance results
associated with these.
2) Enable/disable swapping.
vm.swapping_enabled = 1, default.
vm.swapping_enabled = 0, useful for cases where swapping
degrades performance.
The config option "NO_SWAPPING" is still operative, and
takes precedence over the sysctl. If "NO_SWAPPING" is
specified, the sysctl still exists, but "vm.swapping_enabled"
is hard-wired to "0".
Each of these can be changed "on the fly."
1) Make it much less likely to miss a wakeup in vm_page_free_wakeup
2) Create a new entry point into pmap: pmap_ts_referenced, eliminates
the need to scan the pv lists twice in many cases. Perhaps there
is alot more to do here to work on minimizing pv list manipulation
3) Minor improvements to vm_pageout including the use of pmap_ts_ref.
4) Major changes and code improvement to pmap. This code has had
several serious bugs in page table page manipulation. In order
to simplify the problem, and hopefully solve it for once and all,
page table pages are no longer "managed" with the pv list stuff.
Page table pages are only (mapped and held/wired) or
(free and unused) now. Page table pages are never inactive,
active or cached. These changes have probably fixed the
hold count problems, but if they haven't, then the code is
simpler anyway for future bugfixing.
5) The pmap code has been sorely in need of re-organization, and I
have taken a first (of probably many) steps. Please tell me
if you have any ideas.
1) Remove potential race conditions on waking up in vm_page_free_wakeup
by making sure that it is at splvm().
2) Fix another bug in vm_map_simplify_entry.
3) Be more complete about converting from default to swap pager
when an object grows to be large enough that there can be
a problem with data structure allocation under low memory
conditions.
4) Make some madvise code more efficient.
5) Added some comments.
queue in vm_fault.
Move the PG_BUSY in vm_fault to the correct place.
Remove redundant/unnecessary code in pmap.c.
Properly block on rundown of page table pages, if they are busy.
I think that the VM system is in pretty good shape now, and the following
individuals (among others, in no particular order) have helped with this
recent bunch of bugs, thanks! If I left anyone out, I apologize!
Stephen McKay, Stephen Hocking, Eric J. Chet, Dan O'Brien, James Raynard,
Marc Fournier.
some problems with the page-table page management code, since it can't
deal with the notion of page-table pages being paged out or in transit.
Also, clean up some stylistic issues per some suggestions from
Stephen McKay.
queue corruption problems, and to apply Gary Palmer's code cleanups.
David Greenman helped with these problems also. There is still
a hang problem using X in small memory machines.
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.
