instead to properly handle any waiters.
Added comments, added support for M_ASLEEP. Generally treat M_ flags
as flags instead of constants to compare against.
and the swap_pager has been completely replaced.
The new swap pager uses the new blist radix-tree based bitmap allocator
for low level swap allocation and deallocation. The new allocator
is effectively O(5) while the old one was O(N), and the new allocator
allocates all required memory at init time rather then at allocate
memory on the fly at run time.
Swap metadata is allocated in clusters and stored in a hash table,
eliminating linearly allocated structures.
Many, many features have been rewritten or added. Swap space is now
reallocated on the fly providing a poor-mans auto defragmentation of
swap space. Swap space that is no longer needed is freed on a timely
basis so no garbage collection is necessary.
Swap I/O is marked B_ASYNC and NFS has been fixed to do the right
thing with it, so NFS-based paging now has around 10x the performance
as it did before ( previously NFS enforced synchronous I/O for paging ).
changes to the VM system to support the new swapper, VM bug
fixes, several VM optimizations, and some additional revamping of the
VM code. The specific bug fixes will be documented with additional
forced commits. This commit is somewhat rough in regards to code
cleanup issues.
Reviewed by: "John S. Dyson" <root@dyson.iquest.net>, "David Greenman" <dg@root.com>
shared signal handling when there is shared signal handling being
used.
This removes the main objection to making the shared signal handling
a standard ability in rfork() and friends and 'unconditionalising'
this code. (i.e. the allocation of an extra 328 bytes per process).
Signal handling information remains in the U area until such a time as
it's reference count would be incremented to > 1. At that point a new
struct is malloc'd and maintained in KVM so that it can be shared between
the processes (threads) using it.
A function to check the reference count and move the struct back to the U
area when it drops back to 1 is also supplied. Signal information is
therefore now swapable for all processes that are not sharing that
information with other processes. THis should addres the concerns raised
by Garrett and others.
Submitted by: "Richard Seaman, Jr." <dick@tar.com>
downward growing stacks more general.
Add (but don't activate) code to use the new stack facility
when running threads, (specifically the linux threads support).
This allows people to use both linux compiled linuxthreads, and also the
native FreeBSD linux-threads port.
The code is conditional on VM_STACK. Not using this will
produce the old heavily tested system.
Submitted by: Richard Seaman <dick@tar.com>
"dying daemons" problem. (I thought this code was introduced in rev.1.80,
but it just relaxed the condition.)
Also, kill related "suggest more swap space" warning (also introduced in
1.80). It was confusing, to say the least...
Requested by: msmith
Not objected by: dg
Submitted by: "Richard Seaman, Jr." <lists@tar.com>
Obtained from: linux :-)
Code to allow Linux Threads to run under FreeBSD.
By default not enabled
This code is dependent on the conditional
COMPAT_LINUX_THREADS (suggested by Garret)
This is not yet a 'real' option but will be within some number of hours.
for possible buffer overflow problems. Replaced most sprintf()'s
with snprintf(); for others cases, added terminating NUL bytes where
appropriate, replaced constants like "16" with sizeof(), etc.
These changes include several bug fixes, but most changes are for
maintainability's sake. Any instance where it wasn't "immediately
obvious" that a buffer overflow could not occur was made safer.
Reviewed by: Bruce Evans <bde@zeta.org.au>
Reviewed by: Matthew Dillon <dillon@apollo.backplane.com>
Reviewed by: Mike Spengler <mks@networkcs.com>
almost always causes this panic for the curproc != pageproc case.
This case apparently doesn't happen in normal operation, but it
happens when vm_page_alloc_contig() is called when there is a memory
hogging application that hasn't already been paged out.
PR: 8632
Reviewed by: info@opensound.com (Dev Mazumdar), dg
Broken in: rev.1.89 (1998/02/23)
truncated to 32 bits.
* Change the calling convention of the device mmap entry point to
pass a vm_offset_t instead of an int for the offset allowing
devices with a larger memory map than (1<<32) to be supported
on the alpha (/dev/mem is one such).
These changes are required to allow the X server to mmap the various
I/O regions used for device port and memory access on the alpha.
file to a stream socket. sendfile(2) is similar to implementations in
HP-UX, Linux, and other systems, but the API is more extensive and
addresses many of the complaints that the Apache Group and others have
had with those other implementations. Thanks to Marc Slemko of the
Apache Group for helping me work out the best API for this.
Anyway, this has the "net" result of speeding up sends of files over
TCP/IP sockets by about 10X (that is to say, uses 1/10th of the CPU
cycles) when compared to a traditional read/write loop.
when bdevsw[] became sparse. We still depend on magic to avoid having to
check that (v_rdev) device numbers in vnodes are not NODEV.
Removed a redundant `major(dev) < nblkdev' test instead of updating it.
Don't follow a garbage bdevsw pointer for attempts to swap on empty
regular files. This case currently can't happen. Swapping on regular
files is ifdefed out in swapon() and isn't attempted for empty files
in nfs_mountroot().
needs to be called prior to freeing remaining pages in the object so that
the device pager has an opportunity to grab its "fake" pages. Also, in
the case of wired pages, the page must be made busy prior to calling
vm_page_remove. This is a difference from 2.2.x that I overlooked when
I brought these changes forward.
legitimately wired pages. Currently we print a diagnostic when this
happens, but this will be removed soon when it will be common for this
to occur with zero-copy TCP/IP buffers.
1) The vnode pager wasn't properly tracking the file size due to
"size" being page rounded in some cases and not in others.
This sometimes resulted in corrupted files. First noticed by
Terry Lambert.
Fixed by changing the "size" pager_alloc parameter to be a 64bit
byte value (as opposed to a 32bit page index) and changing the
pagers and their callers to deal with this properly.
2) Fixed a bogus type cast in round_page() and trunc_page() that
caused some 64bit offsets and sizes to be scrambled. Removing
the cast required adding casts at a few dozen callers.
There may be problems with other bogus casts in close-by
macros. A quick check seemed to indicate that those were okay,
however.
simple-lock.
The reviewer raises the following caveat: "I believe these changes
open a non-critical race condition when adding memory to the pool
for the zone. I think what will happen is that you could have two
threads that are simultaneously adding additional memory when the
pool runs out. This appears to not be a problem, however, since
the re-aquisition of the lock will protect the list pointers."
The submitter agrees that the race is non-critical, and points out
that it already existed for the non-SMP case. He suggests that
perhaps a sleep lock (using the lock manager) should be used to
close that race. This might be worth revisiting after 3.0 is
released.
Reviewed by: dg (David Greenman)
Submitted by: tegge (Tor Egge)
expected. This bug caused builds of Modula-3 to fail in mysterious
ways on SMP kernels. More precisely, such builds failed on systems
with kern.fast_vfork equal to 0, the default and only supported
value for SMP kernels.
PR: kern/7468
Submitted by: tegge (Tor Egge)
when nfs is an LKM. Declare it in a header file. Don't forget to use
it in non-Lite2 code. Initialize it to -1 instead of to 0, since 0
will soon be the mount type number for the first vfs loaded.
NetBSD uses strcmp() to avoid this ugly global.
Add some overflow checks to read/write (from bde).
Change all modifications to vm_page::flags, vm_page::busy, vm_object::flags
and vm_object::paging_in_progress to use operations which are not
interruptable.
Reviewed by: Bruce Evans <bde@zeta.org.au>
managed to avoid corruption of this variable by luck (the compiler used a
memory read-modify-write instruction which wasn't interruptable) but other
architectures cannot.
With this change, I am now able to 'make buildworld' on the alpha (sfx: the
crowd goes wild...)
code still left in there. The macros it describes disapeared some-
time since 4.4BSD lite.
PR: 7246
Reviewed by: phk
Submitted by: Stefan Eggers <seggers@semyam.dinoco.de>
respectively. Most of the longs should probably have been
u_longs, but this changes is just to prevent warnings about
casts between pointers and integers of different sizes, not
to fix poorly chosen types.
casting them to long, etc. Fixed some nearby printf bogons (sign
errors not warned about by gcc, and style bugs, but not truncation
of vm_ooffset_t's).
casting them to long, etc. Fixed some nearby printf bogons (sign
errors not warned about by gcc, and style bugs, but not truncation
of vm_ooffset_t's).
Use slightly less bogus casts for passing pointers to ddb command
functions.
There is only cdevsw (which should be renamed in a later edit to deventry
or something). cdevsw contains the union of what were in both bdevsw an
cdevsw entries. The bdevsw[] table stiff exists and is a second pointer
to the cdevsw entry of the device. it's major is in d_bmaj rather than
d_maj. some cleanup still to happen (e.g. dsopen now gets two pointers
to the same cdevsw struct instead of one to a bdevsw and one to a cdevsw).
rawread()/rawwrite() went away as part of this though it's not strictly
the same patch, just that it involves all the same lines in the drivers.
cdroms no longer have write() entries (they did have rawwrite (?)).
tapes no longer have support for bdev operations.
Reviewed by: Eivind Eklund and Mike Smith
Changes suggested by eivind.
as the value in b_vp is often not really what you want.
(and needs to be frobbed). more cleanups will follow this.
Reviewed by: Bruce Evans <bde@freebsd.org>
FreeBSD/alpha. The most significant item is to change the command
argument to ioctl functions from int to u_long. This change brings us
inline with various other BSD versions. Driver writers may like to
use (__FreeBSD_version == 300003) to detect this change.
The prototype FreeBSD/alpha machdep will follow in a couple of days
time.
printf() of "Out of mbuf clusters - adjust NMBCLUSTERS or increase
maxusers" so that the message is more informative and so that it will
appear in the kernel message buffer.
unexpectedly do not complete writes even with sync I/O requests.
This should help the behavior of mmaped files when using
softupdates (and perhaps in other circumstances also.)
the page offset. If a large file offset was passed in, a large negative
array index could be generated which could cause page faults etc at worst
and file corruption at the least. (Pages are allocated within file
space on page alignment boundaries, so a file offset being passed in here
is harmless to DTRT. The case where this was happening has already been
fixed though, this is in case it happens again).
Reviewed by: dyson
deallocation cycles. This should provide a measurable improvement
on swap and memory allocation on loaded systems. It is unlikely a
complete solution. Also, provide more map info with procfs.
Chuck Cranor spurred on this improvement.
"time" wasn't a atomic variable, so splfoo() protection were needed
around any access to it, unless you just wanted the seconds part.
Most uses of time.tv_sec now uses the new variable time_second instead.
gettime() changed to getmicrotime(0.
Remove a couple of unneeded splfoo() protections, the new getmicrotime()
is atomic, (until Bruce sets a breakpoint in it).
A couple of places needed random data, so use read_random() instead
of mucking about with time which isn't random.
Add a new nfs_curusec() function.
Mark a couple of bogosities involving the now disappeard time variable.
Update ffs_update() to avoid the weird "== &time" checks, by fixing the
one remaining call that passwd &time as args.
Change profiling in ncr.c to use ticks instead of time. Resolution is
the same.
Add new function "tvtohz()" to avoid the bogus "splfoo(), add time, call
hzto() which subtracts time" sequences.
Reviewed by: bde
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.
1) When freeing pages, it is a good idea to protect them off.
(This is probably gratuitious, but good form.)
2) Allow collapsing pages in the backing object that are
PQ_CACHE. This will improve memory utilization.
3) Correct the collapse code so that pages that were on the
cache queue are moved to the inactive queue. This is
done when pages are marked dirty (so that those pages
will be properly paged out instead of freed), so that
cached pages will not be paradoxically marked dirty.
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.
put alot of it's context into a data structure. This allows
significant shortening of its codepath, and will significantly
decrease it's cache footprint.
Also, add some stats to vmmeter. Note that you'll have to
rebuild/recompile vmstat, systat, etc... Otherwise, you'll
get "very interesting" paging stats.
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."
These diffs implement the first stage of a VOP_{GET|PUT}PAGES pushdown
for local media FS's.
See ffs_putpages in /sys/ufs/ufs/ufs_readwrite.c for implementation
details for generic *_{get|put}pages for local media FS's. Support
is trivial to add for any FS that formerly relied on the default
behaviour of the vnode_pager in in EOPNOTSUPP cases (just copy the
ffs_getpages() code for the FS in question's *_{get|put}pages).
Obviously, it would be better if each local media FS implemented a
more optimal method, instead of calling an exported interface from
the /sys/vm/vnode_pager.c, but this is a necessary first step in
getting the FS's to a point where they can be supplied with better
implementations on a case-by-case basis.
Obviously, the cd9660_putpages() can be rather trivial (since it
is a read-only FS type 8-)).
A slight (temporary) modification is made to print a diagnostic message
in the case where the underlying filesystem attempts to engage in the
previous behaviour. Failure is likely to be ungraceful.
Submitted by: terry@freebsd.org (Terry Lambert)
improve tuning on larger systems. (A couple of the VM tuning params for
small systems were so badly chosen that the system could hang under load.)
The broken tuning was originaly my fault.
have declined due to code-rot over time. The swap pager rundown code
has been clean-up, and unneeded wakeups removed. Lots of splbio's
are changed to splvm's. Also, set the dynamic tunables for the
pageout daemon to be more sane for larger systems (thereby decreasing
the daemon overheadla.)
in a way identically as before.) I had problems with the system properly
handling the number of vnodes when there is alot of system memory, and the
default VM_KMEM_SIZE. Two new options "VM_KMEM_SIZE_SCALE" and
"VM_KMEM_SIZE_MAX" have been added to support better auto-sizing for systems
with greater than 128MB.
Add some accouting for vm_zone memory allocations, and provide properly
for vm_zone allocations out of the kmem_map. Also move the vm_zone
allocation stats to the VM OID tree from the KERN OID tree.
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.
This introduce an xxxFS_BOOT for each of the rootable filesystems.
(Presently not required, but encouraged to allow a smooth move of option *FS
to opt_dontuse.h later.)
LFS is temporarily disabled, and will be re-enabled tomorrow.
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.
original BSD code. The association between the vnode and the vm_object
no longer includes reference counts. The major difference is that
vm_object's are no longer freed gratuitiously from the vnode, and so
once an object is created for the vnode, it will last as long as the
vnode does.
When a vnode object reference count is incremented, then the underlying
vnode reference count is incremented also. The two "objects" are now
more intimately related, and so the interactions are now much less
complex.
When vnodes are now normally placed onto the free queue with an object still
attached. The rundown of the object happens at vnode rundown time, and
happens with exactly the same filesystem semantics of the original VFS
code. There is absolutely no need for vnode_pager_uncache and other
travesties like that anymore.
A side-effect of these changes is that SMP locking should be much simpler,
the I/O copyin/copyout optimizations work, NFS should be more ponderable,
and further work on layered filesystems should be less frustrating, because
of the totally coherent management of the vnode objects and vnodes.
Please be careful with your system while running this code, but I would
greatly appreciate feedback as soon a reasonably possible.
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.
noticed some major enhancements available for UP situations. The number
of UP TLB flushes is decreased much more than significantly with these
changes. Since a TLB flush appears to cost minimally approx 80 cycles,
this is a "nice" enhancement, equiv to eliminating between 40 and 160
instructions per TLB flush.
Changes include making sure that kernel threads all use the same PTD,
and eliminate unneeded PTD switches at context switch time.
is apparently useful for large shell systems, or systems with long running
idle processes. To enable the feature:
sysctl -w vm.swap_idle_enabled=1
Please note that some of the other vm sysctl variables have been renamed
to be more accurate.
Submitted by: Much of it from Matt Dillon <dillon@best.net>
the maximum pageout rate:
sysctl -w vm.vm_maxlaunder=n
1 < n < inf.
If paging heavily on large systems, it is likely that a performance
improvement can be achieved by increasing the parameter. On a large
system, the parm is 32, but numbers as large as 128 can make a big
difference. If paging is expensive, you might try decreasing the
number to 1-8.
sysctl -w vm.defer_swap_pageouts=1
Causes the system to resist the use of swap space. In low memory
conditions, performance will decrease.
sysctl -w vm.disable_swap_pageouts=1
Causes the system to mostly disable the use of swap space. In
low memory conditions, the system will likely start killing
processes.
