mutexes, which offers lower overhead on both UP and SMP. When allocating
from or freeing to the per-cpu cache, without INVARIANTS enabled, we now
no longer perform any mutex operations, which offers a 1%-3% performance
improvement in a variety of micro-benchmarks. We rely on critical
sections to prevent (a) preemption resulting in reentrant access to UMA on
a single CPU, and (b) migration of the thread during access. In the event
we need to go back to the zone for a new bucket, we release the critical
section to acquire the global zone mutex, and must re-acquire the critical
section and re-evaluate which cache we are accessing in case migration has
occured, or circumstances have changed in the current cache.
Per-CPU cache statistics are now gathered lock-free by the sysctl, which
can result in small races in statistics reporting for caches.
Reviewed by: bmilekic, jeff (somewhat)
Tested by: rwatson, kris, gnn, scottl, mike at sentex dot net, others
the number of entries in exec_map (maximum number of simultaneous execs
that can be handled by the kernel). The default value of 16 is
insufficient on heavily loaded machines (particularly SMP machines), and
if it is exceeded then executing further processes will generate a SIGABRT.
This is a workaround until a better solution can be implemented.
Reviewed by: alc
MFC after: 3 days
of physical addresses. The pages containing these physical addresses will
not be added to the free list and thus will effectively be ignored by the
VM system. This is mostly useful for the case when one knows of specific
physical addresses that have bit errors (such as from a memtest run) so
that one can blacklist the bad pages while waiting for the new sticks of
RAM to arrive. The physical addresses of any ignored pages are listed in
the message buffer as well.
MAP_SHARED so that the entry point gets executed un-conditionally.
This may be useful for security policies which want to perform access
control checks around run-time linking.
-add the mmap(2) flags argument to the check_vnode_mmap entry point
so that we can make access control decisions based on the type of
mapped object.
-update any dependent API around this parameter addition such as
function prototype modifications, entry point parameter additions
and the inclusion of sys/mman.h header file.
-Change the MLS, BIBA and LOMAC security policies so that subject
domination routines are not executed unless the type of mapping is
shared. This is done to maintain compatibility between the old
vm_mmap_vnode(9) and these policies.
Reviewed by: rwatson
MFC after: 1 month
down. If we have dirty pages, the putpages routine will need to know
what the vnode's object is so that it may write out dirty pages.
Pointy hat: phk
Found by: obrien
the type of object represented by the handle argument.
- Allow vm_mmap() to map device memory via cdev objects in addition to
vnodes and anonymous memory. Note that mmaping a cdev directly does not
currently perform any MAC checks like mapping a vnode does.
- Unbreak the DRM getbufs ioctl by having it call vm_mmap() directly on the
cdev the ioctl is acting on rather than trying to find a suitable vnode
to map from.
Reviewed by: alc, arch@
queues lock in vm_object_backing_scan(). Updates to the page's PG_BUSY
flag and busy field are synchronized by the containing object's lock.
Testing the page's hold_count and wire_count in vm_object_backing_scan()'s
OBSC_COLLAPSE_NOWAIT case is unnecessary. There is no reason why the held
or wired pages cannot be migrated to the shadow object.
Reviewed by: tegge
is inserted.
- In vm_page_remove() drop the backing vnode when the last page
is removed.
- Don't check the vnode to see if it must be reclaimed on every
call to vm_page_free_toq() as we only check it now when it is
actually required. This saves us two lock operations per call.
Sponsored by: Isilon Systems, Inc.
patch from kan@).
Pull bufobj_invalbuf() out of vinvalbuf() and make g_vfs call it on
close. This is not yet a generally safe function, but for this very
specific use it is safe. This solves the problem with buffers not
being flushed by unmount or after failed mount attempts.
statement from some files, so re-add it for the moment, until the
related legalese is sorted out. This change affects:
sys/kern/kern_mbuf.c
sys/vm/memguard.c
sys/vm/memguard.h
sys/vm/uma.h
sys/vm/uma_core.c
sys/vm/uma_dbg.c
sys/vm/uma_dbg.h
sys/vm/uma_int.h
UMA_ZONE_REFCNT and UMA_ZONE_MALLOC zones, as the page(s) undoubtedly
came from kmem_map for those two. Previously it would set it back
to NULL for UMA_ZONE_REFCNT zones and although this was probably not
fatal, it added MORE code for no reason.
an unused pageq queue reference in the page structure to stash a pointer
to the MemGuard FIFO. Using the page->object field caused problems
because when vm_map_protect() was called the second time to set
VM_PROT_DEFAULT back onto a set of pages in memguard_map, the protection
in the VM would be changed but the PMAP code would lazily not restore
the PG_RW bit on the underlying pages right away (see pmap_protect()).
So when a page fault finally occured and the VM noticed the faulting
address corresponds to a page that _does_ have write access now, it
would then call into PMAP to set back PG_RW (i386 case being discussed
here). However, before it got to do that, an assertion on the object
lock not being owned would get triggered, as the object of the faulting
page would need to be locked but was overloaded by MemGuard. This is
precisely why MemGuard cannot overload page->object.
Submitted by: Alan Cox (alc@)
a little bit of complexity but performance requirements lacking (this is
a debugging allocator after all), it's really not too bad (still
only 317 lines).
Also add an additional check to help catch really weird 3-threads-involved
races: make memguard_free() write to the first page handed back, always,
before it does anything else.
Note that there is still a problem in VM+PMAP (specifically with
vm_map_protect) w.r.t. MemGuard uses it, but this will be fixed shortly
and this change stands on its own.
the name Sande^H^H^H^H^Hvnode_create_vobject().
Make the new function take a size argument which removes the need for
a VOP_STAT() or a very pessimistic guess for disks.
Call that new function from vop_stdcreatevobject().
Make vnode_pager_alloc() private now that its only user came home.
- Use VFS_LOCK_GIANT() rather than directly acquiring giant in places
where giant is only held because vfs requires it.
Sponsored By: Isilon Systems, Inc.
designed to help detect tamper-after-free scenarios, a problem more
and more common and likely with multithreaded kernels where race
conditions are more prevalent.
Currently MemGuard can only take over malloc()/realloc()/free() for
particular (a) malloc type(s) and the code brought in with this
change manually instruments it to take over M_SUBPROC allocations
as an example. If you are planning to use it, for now you must:
1) Put "options DEBUG_MEMGUARD" in your kernel config.
2) Edit src/sys/kern/kern_malloc.c manually, look for
"XXX CHANGEME" and replace the M_SUBPROC comparison with
the appropriate malloc type (this might require additional
but small/simple code modification if, say, the malloc type
is declared out of scope).
3) Build and install your kernel. Tune vm.memguard_divisor
boot-time tunable which is used to scale how much of kmem_map
you want to allott for MemGuard's use. The default is 10,
so kmem_size/10.
ToDo:
1) Bring in a memguard(9) man page.
2) Better instrumentation (e.g., boot-time) of MemGuard taking
over malloc types.
3) Teach UMA about MemGuard to allow MemGuard to override zone
allocations too.
4) Improve MemGuard if necessary.
This work is partly based on some old patches from Ian Dowse.
and BBO is BO's backing object. Now, suppose that O and BO are being
collapsed. Furthermore, suppose that BO has been marked dead
(OBJ_DEAD) by vm_object_backing_scan() and that either
vm_object_backing_scan() has been forced to sleep due to encountering
a busy page or vm_object_collapse() has been forced to sleep due to
memory allocation in the swap pager. If vm_object_deallocate() is
then called on BBO and BO is BBO's only shadow object,
vm_object_deallocate() will collapse BO and BBO. In doing so, it adds
a necessary temporary reference to BO. If this collapse also sleeps
and the prior collapse resumes first, the temporary reference will
cause vm_object_collapse to panic with the message "backing_object %p
was somehow re-referenced during collapse!"
Resolve this race by changing vm_object_deallocate() such that it
doesn't collapse BO and BBO if BO is marked dead. Once O and BO are
collapsed, vm_object_collapse() will attempt to collapse O and BBO.
So, vm_object_deallocate() on BBO need do nothing.
Reported by: Peter Holm on 20050107
URL: http://www.holm.cc/stress/log/cons102.html
In collaboration with: tegge@
Candidate for RELENG_4 and RELENG_5
MFC after: 2 weeks
I'm not sure why a credential was added to these in the first place, it is
not used anywhere and it doesn't make much sense:
The credentials for syncing a file (ability to write to the
file) should be checked at the system call level.
Credentials for syncing one or more filesystems ("none")
should be checked at the system call level as well.
If the filesystem implementation needs a particular credential
to carry out the syncing it would logically have to the
cached mount credential, or a credential cached along with
any delayed write data.
Discussed with: rwatson
recursion from the VM is handled (and the calling code that allocates
buckets knows how to deal with it), we do not want to prevent allocation
from the slab header zones (slabzone and slabrefzone) if uk_recurse is
not zero for them. The reason is that it could lead to NULL being
returned for the slab header allocations even in the M_WAITOK
case, and the caller can't handle that (this is also explained in a
comment with this commit).
The problem analysis is documented in our mailing lists:
http://docs.freebsd.org/cgi/getmsg.cgi?fetch=153445+0+archive/2004/freebsd-current/20041231.freebsd-current
(see entire thread for proper context).
Crash dump data provided by: Peter Holm <peter@holm.cc>
queue and (possibly) unlocking the containing object from
vm_page_alloc() to vm_page_select_cache(). Recent optimizations to
vm_map_pmap_enter() (see vm_map.c revisions 1.362 and 1.363) and
pmap_enter_quick() have resulted in panic()s because vm_page_alloc()
mistakenly unlocked objects that had not been locked by
vm_page_select_cache().
Reported by: Peter Holm and Kris Kennaway
queue to the free queue. With this change, if a page from the cache
queue belongs to a locked object, it is simply skipped over rather
than moved to the inactive queue.
flag and busy field with the global page queues lock to synchronizing their
access with the containing object's lock. Specifically, acquire the
containing object's lock before reading the page's PG_BUSY flag and busy
field in vm_fault().
Reviewed by: tegge@
on entry and it assumes the responsibility for releasing the page queues
lock if it must sleep.
Remove a bogus comment from pmap_enter_quick().
Using the first change, modify vm_map_pmap_enter() so that the page queues
lock is acquired and released once, rather than each time that a page
is mapped.
In such cases, the busying of the page and the unlocking of the
containing object by vm_map_pmap_enter() and vm_fault_prefault() is
unnecessary overhead. To eliminate this overhead, this change
modifies pmap_enter_quick() so that it expects the object to be locked
on entry and it assumes the responsibility for busying the page and
unlocking the object if it must sleep. Note: alpha, amd64, i386 and
ia64 are the only implementations optimized by this change; arm,
powerpc, and sparc64 still conservatively busy the page and unlock the
object within every pmap_enter_quick() call.
Additionally, this change is the first case where we synchronize
access to the page's PG_BUSY flag and busy field using the containing
object's lock rather than the global page queues lock. (Modifications
to the page's PG_BUSY flag and busy field have asserted both locks for
several weeks, enabling an incremental transition.)
revision 1.55, the address parameter to vnode_pager_addr() was changed
from an unsigned 32-bit quantity to a signed 64-bit quantity. However,
an out-of-range check on the address was not updated. Consequently,
memory-mapped I/O on files greater than 2GB could cause a kernel panic.
Since the address is now a signed 64-bit quantity, the problem resolution
is simply to remove a cast.
Reviewed by: bde@ and tegge@
PR: 73010
MFC after: 1 week
to implement the sanity check should have been changed when we converted
the implementation of vm_pindex_t from 32 to 64 bits. (Thus, RELENG_4 is
not affected.) The consequence of this error would be a legimate write to
an extremely large file being treated as an errant attempt to write meta-
data.
Discussed with: tegge@
Historically, our contigmalloc1() and contigmalloc2() assumes
that a page in PQ_CACHE can be unconditionally reused by busying
and freeing it. Unfortunatelly, when object happens to be not
NULL, the code will set m->object to NULL and disregard the fact
that the page is actually in the VM page bucket, resulting in
page bucket hash table corruption and finally, a filesystem
corruption, or a 'page not in hash' panic.
This commit has borrowed the idea taken from DragonFlyBSD's fix
to the VM fix by Matthew Dillon[1]. This version of patch will
do the following checks:
- When scanning pages in PQ_CACHE, check hold_count and
skip over pages that are held temporarily.
- For pages in PQ_CACHE and selected as candidate of being
freed, check if it is busy at that time.
Note: It seems that this is might be unrelated to kern/72539.
Obtained from: DragonFlyBSD, sys/vm/vm_contig.c,v 1.11 and 1.12 [1]
Reminded by: Matt Dillon
Reworked by: alc
MFC After: 1 week
instead of a vnode for it.
The vnode_pager does not and should not have any interest in what
the filesystem uses for backend.
(vfs_cluster doesn't use the backing store argument.)
includes the latter, but also declares variables which are defined
in kern/subr_param.c).
Change som VM parameters from quad_t to unsigned long. They refer to
quantities (size limits for text, heap and stack segments) which must
necessarily be smaller than the size of the address space, so long is
adequate on all platforms.
MFC after: 1 week
number of entries into bucket_zone_lookup(), which helps make more
clear the logic of consumers of bucket zones.
Annotate the behavior of bucket_init() with a comment indicating
how the various data structures, including the bucket lookup tables,
are initialized.
swapoff: failed to locate %d swap blocks
The race occurred because putpages() can block between the time it
allocates swap space and the time it updates the swap metadata to
associate that space with a vm_object, so swapoff() would complain
about the temporary inconsistency. I hoped to fix this by making
swp_pager_getswapspace() and swp_pager_meta_build() a single atomic
operation, but that proved to be inconvenient. With this change,
swapoff() simply doesn't attempt to be so clever about detecting when
all the pageout activity to the target device should have drained.
because this call is only needed to wake threads that slept when they
discovered a dead object connected to a vnode. To eliminate unnecessary
calls to wakeup() by vnode_pager_dealloc(), introduce a new flag,
OBJ_DISCONNECTWNT.
Reviewed by: tegge@
thread is created rather than adjusting the priority in the main
function. (kthread_create() should probably take the initial priority
as an argument.)
- Only yield the CPU in the !PREEMPTION case if there are any other
runnable threads. Yielding when there isn't anything else better to do
just wastes time in pointless context switches (albeit while the system
is idle.)
In order to avoid livelock, swapoff() skips over objects with a
nonzero pip count and makes another pass if necessary. Since it is
impossible to know which objects we care about, it would choose an
arbitrary object with a nonzero pip count and wait for it before
making another pass, the theory being that this object would finish
paging about as quickly as the ones we care about. Unfortunately,
we may have slept since we acquired a reference to this object.
Hack around this problem by tsleep()ing on the pointer anyway, but
timeout after a fixed interval. More elegant solutions are possible,
but the ones I considered unnecessarily complicate this rare case.
Also, kill some nits that seem to have crept into the swapoff() code
in the last 75 revisions or so:
- Don't pass both sp and sp->sw_used to swap_pager_swapoff(), since
the latter can be derived from the former.
- Replace swp_pager_find_dev() with something simpler. There's no
need to iterate over the entire list of swap devices just to determine
if a given block is assigned to the one we're interested in.
- Expand the scope of the swhash_mtx in a couple of places so that it
isn't released and reacquired once for every hash bucket.
- Don't drop the swhash_mtx while holding a reference to an object.
We need to lock the object first. Unfortunately, doing so would
violate the established lock order, so use VM_OBJECT_TRYLOCK() and
try again on a subsequent pass if the object is already locked.
- Refactor swp_pager_force_pagein() and swap_pager_swapoff() a bit.
need for most calls to vm_page_busy(). Specifically, most calls to
vm_page_busy() occur immediately prior to a call to vm_page_remove().
In such cases, the containing vm object is locked across both calls.
Consequently, the setting of the vm page's PG_BUSY flag is not even
visible to other threads that are following the synchronization
protocol.
This change (1) eliminates the calls to vm_page_busy() that
immediately precede a call to vm_page_remove() or functions, such as
vm_page_free() and vm_page_rename(), that call it and (2) relaxes the
requirement in vm_page_remove() that the vm page's PG_BUSY flag is
set. Now, the vm page's PG_BUSY flag is set only when the vm object
lock is released while the vm page is still in transition. Typically,
this is when it is undergoing I/O.
IF INVARIANTS is defined, and in the rare case that we have
allocated some objects from the slab and at least one initializer
on at least one of those objects failed, and we need to fail the
allocation and push the uninitialized items back into the slab
caches -- in that scenario, we would fail to [re]set the
bucket cache's ub_bucket item references to NULL, which would
eventually trigger a KASSERT.
We keep si_bsize_phys around for now as that is the simplest way to pull
the number out of disk device drivers in devfs_open(). The correct solution
would be to do an ioctl(DIOCGSECTORSIZE), but the point is probably mooth
when filesystems sit on GEOM, so don't bother for now.
