Before this change a copy operation with cp(1) would not update the
file access times.
According to the POSIX mmap(2) documentation: the st_atime field
of the mapped file may be marked for update at any time between the
mmap() call and the corresponding munmap() call. The initial read
or write reference to a mapped region shall cause the file's st_atime
field to be marked for update if it has not already been marked for
update.
I'm not sure this is the right thing to do, but at least I don't panic
anymore when swapping on a NFS file without using md(4).
X-MFC after: proper review
UMA boot pages.
Disable recursion on the general UMA lock now that startup_alloc() no
longer uses it.
Eliminate the variable uma_boot_free. It serves no purpose.
Note: This change eliminates a lock-order reversal between a system
map mutex and the UMA lock. See
http://sources.zabbadoz.net/freebsd/lor.html#109 for details.
MFC after: 3 days
vm_pager_init() is run before required nswbuf variable has been set
to correct value. This caused system to run with single pbuf available
for vnode_pager. Handle both cluster_pbuf_freecnt and vnode_pbuf_freecnt
variable in the same way.
Reported by: ade
Obtained from: alc
MFC after: 2 days
due to the vm object being locked.
When a process writes large amounts of data to a file, the vm object associated
with that file can contain most of the physical pages on the machine. If the
process is preempted while holding the lock on the vm object, pagedaemon would
be able to move very few pages from PQ_INACTIVE to PQ_CACHE or from PQ_ACTIVE
to PQ_INACTIVE, resulting in unlimited cleaning of dirty pages belonging to
other vm objects.
Temporarily unlock the page queues lock while locking vm objects to avoid lock
order violation. Detect and handle relevant page queue changes.
This change depends on both the lock portion of struct vm_object and normal
struct vm_page being type stable.
Reviewed by: alc
as opt_vmpage.h will not be available to user space library builds. A
similar existing check is present for KLD_MODULE for similar reasons.
MFC after: 3 days
monitoring API, which might or might not be the same as the internal
maximum (currently none).
Export flag information on UMA zones -- in particular, whether or
not this is a secondary zone, and so the keg free count should be
considered in that light.
MFC after: 1 day
make the b_iodone callback responsible for setting it if it is needed.
Previously, it was set unconditionally by bufdone() without holding
whichever lock is shared by the b_iodone callback and the corresponding
top-half function. Consequently, in a race, the top-half function could
conclude that operation was done before the b_iodone callback finished.
See, for example, aio_physwakeup() and aio_fphysio().
Note: I don't believe that the other, more widely-used b_iodone callbacks
are affected.
Discussed with: jeff
Reviewed by: phk
MFC after: 2 weeks
- Add a new uma_zfree_internal() flag, ZFREE_STATFREE, which causes it to
to update the zone's uz_frees statistic. Previously, the statistic was
updated unconditionally.
- Use the flag in situations where a "real" free occurs: i.e., one where
the caller is freeing an allocated item, to be differentiated from
situations where uma_zfree_internal() is used to tear down the item
during slab teardown in order to invoke its fini() method. Also use
the flag when UMA is freeing its internal objects.
- When exchanging a bucket with the zone from the per-CPU cache when
freeing an item, flush cache statistics back to the zone (since the
zone lock and critical section are both held) to match the allocation
case.
MFC after: 3 days
per-CPU cache statistics. UMA sizes the cache array based on the
number of CPUs at boot (mp_maxid + 1), and iterating based on MAXCPU
could read off the end of the array (into the next zone).
Reported by: yongari
MFC after: 1 week
it covers the following of the uc_alloc/freebucket cache pointers.
Originally, I felt that the race wasn't helped by holding the mutex,
hence a comment in the code and not holding it across the cache access.
However, it does improve consistency, as while it doesn't prevent
bucket exchange, it does prevent bucket pointer invalidation. So a
race in gathering cache free space statistics still can occur, but not
one that follows an invalid bucket pointer, if the mutex is held.
Submitted by: yongari
MFC after: 1 week
fs.first_object->flags & OBJ_NEEDGIANT test that was missed in an earlier
revision. This fixes mutex assertion failures in the debug.mpsafevm=0
case.
Reported by: ps
MFC after: 3 days
statistics via a binary structure stream:
- Add structure 'uma_stream_header', which defines a stream version,
definition of MAXCPUs used in the stream, and the number of zone
records in the stream.
- Add structure 'uma_type_header', which defines the name, alignment,
size, resource allocation limits, current pages allocated, preferred
bucket size, and central zone + keg statistics.
- Add structure 'uma_percpu_stat', which, for each per-CPU cache,
includes the number of allocations and frees, as well as the number
of free items in the cache.
- When the sysctl is queried, return a stream header, followed by a
series of type descriptions, each consisting of a type header
followed by a series of MAXCPUs uma_percpu_stat structures holding
per-CPU allocation information. Typical values of MAXCPU will be
1 (UP compiled kernel) and 16 (SMP compiled kernel).
This query mechanism allows user space monitoring tools to extract
memory allocation statistics in a machine-readable form, and to do so
at a per-CPU granularity, allowing monitoring of allocation patterns
across CPUs in order to better understand the distribution of work and
memory flow over multiple CPUs.
While here, also export the number of UMA zones as a sysctl
vm.uma_count, in order to assist in sizing user swpace buffers to
receive the stream.
A follow-up commit of libmemstat(3), a library to monitor kernel memory
allocation, will occur in the next few days. This change directly
supports converting netstat(1)'s "-mb" mode to using UMA-sourced stats
rather than separately maintained mbuf allocator statistics.
MFC after: 1 week
zone whenever it was moving buckets between the zone and the cache,
or when coalescing statistics across the CPU. Remove flushing of
statistics to the zone when coalescing statistics as part of sysctl,
as we won't be running on the right CPU to write to the cache
statistics.
Add a missed gathering of statistics: when uma_zalloc_internal()
does a special case allocation of a single item, make sure to update
the zone statistics to represent this. Previously this case wasn't
accounted for in user-visible statistics.
MFC after: 1 week
many regions checked again and again despite knowing the pages
contained were not usable and only satisfied the alignment constraints
This case was compounded, especially for large allocations, by the
practice of looping from the top of memory so as to keep out of the
important low-memory regions. While the old contigmalloc(9) has the
same problem, it is not as noticeable due to looping from the low
memory to high.
This degenerate case is fixed, as well as reversing the sense of the
rest of the loops within it, to provide a tremendous speed increase.
This makes the best case O(n * VM overhead) much more likely than the
worst case O(4 * VM overhead). For comparison, the worst case for old
contigmalloc would be O(5 * VM overhead) in addition to its strategy
of turning used memory into free being highly pessimal.
Also, fix a bug that in practice most likely couldn't have been triggered,
int the new contigmalloc(9): it walked backwards from the end of memory
without accounting for how many pages it needed. Potentially, nonexistant
pages could have been mapped. This hasn't occurred because the kernel
generally requests as its first contigmalloc(9) a single page.
Reported by: Nicolas Dehaine <nicko@stbernard.com>, wes
MFC After: 1 month
More testing by: Nicolas Dehaine <nicko@stbernard.com>, wes
vm_page's machine-dependent fields. Use this function in
vm_pageq_add_new_page() so that the vm_page's machine-dependent and
machine-independent fields are initialized at the same time.
Remove code from pmap_init() for initializing the vm_page's
machine-dependent fields.
Remove stale comments from pmap_init().
Eliminate the Boolean variable pmap_initialized from the alpha, amd64,
i386, and ia64 pmap implementations. Its use is no longer required
because of the above changes and earlier changes that result in physical
memory that is being mapped at initialization time being mapped without
pv entries.
Tested by: cognet, kensmith, marcel
underlying vnode requires Giant.
- In vm_fault only acquire Giant if the underlying object has NEEDSGIANT
set.
- In vm_object_shadow inherit the NEEDSGIANT flag from the backing object.
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.
