caller to vm_page_grab(). Although this gives VM_ALLOC_ZERO a
different meaning for vm_page_grab() than for vm_page_alloc(), I feel
such change is necessary to accomplish other goals. Specifically, I
want to make the PG_ZERO flag immutable between the time it is
allocated by vm_page_alloc() and freed by vm_page_free() or
vm_page_free_zero() to avoid locking overheads. Once we gave up on
the ability to automatically recognize a zeroed page upon entry to
vm_page_free(), the ability to mutate the PG_ZERO flag became useless.
Instead, I would like to say that "Once a page becomes valid, its
PG_ZERO flag must be ignored."
would actually map the file with read access enabled. According to
http://www.opengroup.org/onlinepubs/007904975/functions/mmap.html this is
an error. Similarly, an madvise(..., MADV_WILLNEED) would enable read
access on a virtual address range that was PROT_NONE.
The solution implemented herein is (1) to pass a vm_prot_t to
vm_map_pmap_enter() describing the allowed access and (2) to make
vm_map_pmap_enter() responsible for understanding the limitations of
pmap_enter_quick().
Submitted by: "Mark W. Krentel" <krentel@dreamscape.com>
PR: kern/64573
move its declaration to the machine-dependent header file on those
machines that use it. In principle, only i386 should have it.
Alpha and AMD64 should use their direct virtual-to-physical mapping.
- Remove pmap_kenter_temporary() from ia64. It is unused. Approved
by: marcel@
the reduction of the pager map's size by 8M bytes. In other words, eight
megabytes of largely wasted KVA are returned to the kernel map for use
elsewhere.
vm_mmap_vnode function, where we can safely check for a special /dev/zero
case. Rev. 1.180 has reordered checks and introduced a regression.
Submitted by: alc
Was broken by: kan
to mmap it PROT_EXEC. This also depends on the architecture, as some
architextures (e.g. i386) do not distinguish between read and exec pages
Inspired by: http://linux.bkbits.net:8080/linux-2.4/cset@1.1267.1.85
Reviewed by: alc
pmap. For the kernel pmap, Giant is not required. In general, for
other pmaps, Giant is required by i386's pmap_pte() implementation.
Specifically, the use of PMAP2/PADDR2 is synchronized by Giant.
Note: In principle, updates to the kernel pmap's wired count could be
lost without Giant. However, in practice, we never use the kernel
pmap's wired count. This will be resolved when pmap locking appears.
- With the above change, cpu_thread_clean() and uma_large_free() need
not acquire Giant. (The first case is simply the revival of
i386/i386/vm_machdep.c's revision 1.226 by peter.)
ever since alpha/alpha/pmap.c revision 1.81 introduced the list allpmaps,
there has been no reason for having this function on Alpha. Briefly,
when pmap_growkernel() relied upon the list of all processes to find and
update the various pmaps to reflect a growth in the kernel's valid
address space, pmap_init2() served to avoid a race between pmap
initialization and pmap_growkernel(). Specifically, pmap_pinit2() was
responsible for initializing the kernel portions of the pmap and
pmap_pinit2() was called after the process structure contained a pointer
to the new pmap for use by pmap_growkernel(). Thus, an update to the
kernel's address space might be applied to the new pmap unnecessarily,
but an update would never be lost.
introduction of kern_mlock() and kern_munlock() in
src/sys/kern/kern_sysctl.c 1.150
src/sys/vm/vm_extern.h 1.69
src/sys/vm/vm_glue.c 1.190
src/sys/vm/vm_mmap.c 1.179
because different resource limits are appropriate for transient and
"permanent" page wiring requests.
Retain the kern_mlock() and kern_munlock() API in the revived
vslock() and vsunlock() functions.
Combine the best parts of each of the original sets of implementations
with further code cleanup. Make the mclock() and vslock()
implementations as similar as possible.
Retain the RLIMIT_MEMLOCK check in mlock(). Move the most strigent
test, which can return EAGAIN, last so that requests that have no
hope of ever being satisfied will not be retried unnecessarily.
Disable the test that can return EAGAIN in the vslock() implementation
because it will cause the sysctl code to wedge.
Tested by: Cy Schubert <Cy.Schubert AT komquats.com>
unnecessary and wrong. While it is necessary to verify that the page is
still free after dropping and reacquiring the free page queue lock, the
physical contiguity of the page can not change, making this check
unnecessary. This check was wrong in that it could cause an out-of-bounds
array access.
Tested by: rwatson
vm_page_free() is called. The problem with holding this lock is that it is
a spin lock and vm_page_free() may attempt the acquisition of a different
default-type lock.
the syscall arguments and does the suser() permission check, and
kern_mlock(), which does the resource limit checking and calls
vm_map_wire(). Split munlock() in a similar way.
Enable the RLIMIT_MEMLOCK checking code in kern_mlock().
Replace calls to vslock() and vsunlock() in the sysctl code with
calls to kern_mlock() and kern_munlock() so that the sysctl code
will obey the wired memory limits.
Nuke the vslock() and vsunlock() implementations, which are no
longer used.
Add a member to struct sysctl_req to track the amount of memory
that is wired to handle the request.
Modify sysctl_wire_old_buffer() to return an error if its call to
kern_mlock() fails. Only wire the minimum of the length specified
in the sysctl request and the length specified in its argument list.
It is recommended that sysctl handlers that use sysctl_wire_old_buffer()
should specify reasonable estimates for the amount of data they
want to return so that only the minimum amount of memory is wired
no matter what length has been specified by the request.
Modify the callers of sysctl_wire_old_buffer() to look for the
error return.
Modify sysctl_old_user to obey the wired buffer length and clean up
its implementation.
Reviewed by: bms
swap_pager_putpages()'s buffer completion code. Note: the only
difference between swp_pager_sync_iodone() and bdone(), aside from
the locking in the latter, was the unnecessary clearing of B_ASYNC.
- Remove an unnecessary pmap_page_protect() from
swp_pager_async_iodone().
Reviewed by: tegge
result in a panic "vm_page_cache: caching a dirty page, ...": Access to the
page must be restricted or removed before calling vm_page_cache(). This
race condition is identical in nature to that which was addressed by
vm_pageout.c's revision 1.251 and vm_page.c's revision 1.275.
MFC after: 7 days
panic "vm_page_cache: caching a dirty page, ...": Access to the page must
be restricted or removed before calling vm_page_cache(). This race
condition is identical in nature to that which was addressed by
vm_pageout.c's revision 1.251 and vm_page.c's revision 1.275.
Reviewed by: tegge
MFC after: 7 days
could result in a panic "vm_page_cache: caching a dirty page, ...":
Access to the page must be restricted or removed before calling
vm_page_cache(). This race condition is identical in nature to that
which was addressed by vm_pageout.c's revision 1.251.
- Simplify the code surrounding the fix to this same race condition
in vm_pageout.c's revision 1.251. There should be no behavioral
change. Reviewed by: tegge
MFC after: 7 days
shown that it is not useful.
Rename the relative count g_access_rel() function to g_access(), only
the name has changed.
Change all g_access_rel() calls in our CVS tree to call g_access() instead.
Add an #ifndef BURN_BRIDGES #define of g_access_rel() for source
code compatibility.
the added comment for low-level details.) The effect of this race
condition is a panic "vm_page_cache: caching a dirty page, ..."
Reviewed by: tegge
MFC after: 7 days
- struct plimit includes a mutex to protect a reference count. The plimit
structure is treated similarly to struct ucred in that is is always copy
on write, so having a reference to a structure is sufficient to read from
it without needing a further lock.
- The proc lock protects the p_limit pointer and must be held while reading
limits from a process to keep the limit structure from changing out from
under you while reading from it.
- Various global limits that are ints are not protected by a lock since
int writes are atomic on all the archs we support and thus a lock
wouldn't buy us anything.
- All accesses to individual resource limits from a process are abstracted
behind a simple lim_rlimit(), lim_max(), and lim_cur() API that return
either an rlimit, or the current or max individual limit of the specified
resource from a process.
- dosetrlimit() was renamed to kern_setrlimit() to match existing style of
other similar syscall helper functions.
- The alpha OSF/1 compat layer no longer calls getrlimit() and setrlimit()
(it didn't used the stackgap when it should have) but uses lim_rlimit()
and kern_setrlimit() instead.
- The svr4 compat no longer uses the stackgap for resource limits calls,
but uses lim_rlimit() and kern_setrlimit() instead.
- The ibcs2 compat no longer uses the stackgap for resource limits. It
also no longer uses the stackgap for accessing sysctl's for the
ibcs2_sysconf() syscall but uses kernel_sysctl() instead. As a result,
ibcs2_sysconf() no longer needs Giant.
- The p_rlimit macro no longer exists.
Submitted by: mtm (mostly, I only did a few cleanups and catchups)
Tested on: i386
Compiled on: alpha, amd64
when uma_reclaim() was called. This was introduced when the zone
working-set algorithm was removed in favor of using the per cpu caches
as the working set.
"scheduler" here has very little to do with scheduling. It is actually
the swapper, and it really must be the last SYSINIT'ed item like its
comment says, since proc0 metamorphoses into swapper by calling
scheduler() last in mi_start(), and scheduler() never returns.. Rev.1.29
of subr_4bsd.c broke this by adding another SI_ORDER_FIRST item
(kproc_start() for schedcpu_thread() onto the SI_SUB_RUN_SCHEDULER_LIST.
The sorting of SYSINITs with identical orders (at all levels) is
apparently nondeterministic, so this resulted in schedule() sometimes
being called second last and schedcpu_thread() not being called at all.
This quick fix just changes the code to almost match the comment
(SI_ORDER_FIRST -> SI_ORDER_ANY). "LAST" is misspelled "ANY", and
there is no way to ensure that there is only 1 very lst SYSINIT.
A more complete fix would remove the SYSINIT obfuscation.
SW_INVOL. Assert that one of these is set in mi_switch() and propery
adjust the rusage statistics. This is to simplify the large number of
users of this interface which were previously all required to adjust the
proper counter prior to calling mi_switch(). This also facilitates more
switch and locking optimizations.
- Change all callers of mi_switch() to pass the appropriate paramter and
remove direct references to the process statistics.
full state. (When swap is added their state will change appropriately.)
2. Set swap_pager_full and swap_pager_almost_full to the full state when
the last swap device is removed.
Combined these changes eliminate nonsense messages from the kernel on swap-
less machines.
Item 2 submitted by: Divacky Roman <xdivac02@stud.fit.vutbr.cz>
Prodding by: phk
free pages queue. This is presently needed by contigmalloc1().
- Move a sanity check against attempted double allocation of two pages
to the same vm object offset from vm_page_alloc() to vm_page_insert().
This provides better protection because double allocation could occur
through a direct call to vm_page_insert(), such as that by
vm_page_rename().
- Modify contigmalloc1() to hold the mutex synchronizing access to the
free pages queue while it scans vm_page_array in search of free pages.
- Correct a potential leak of pages by contigmalloc1() that I introduced
in revision 1.20: We must convert all cache queue pages to free pages
before we begin removing free pages from the free queue. Otherwise,
if we have to restart the scan because we are unable to acquire the
vm object lock that is necessary to convert a cache queue page to a
free page, we leak those free pages already removed from the free queue.
vm object hasn't changed, the desired page will be at or near the root
of the vm object's splay tree, making vm_page_lookup() cheap. (The only
lock required for vm_page_lookup() is already held.) If, however, the
vm object has changed and retry was requested, eliminating the generation
check also eliminates a pointless acquisition and release of the page
queues lock.
This guard page would have trapped the problems with the MFC of the PAE
support to RELENG_4 at an earlier point in the sequence of events.
Submitted by: tegge
pmap_init(). Such a large preallocation is unnecessary and wastes
nearly eight megabytes of kernel virtual address space per gigabyte
of managed physical memory.
- Increase UMA_BOOT_PAGES by two. This enables the removal of
pmap_pv_allocf(). (Note: this function was only used during
initialization, specifically, after pmap_init() but before
pmap_init2(). During pmap_init2(), a new allocator is installed.)
mincore(2) should check that the page is valid, not just allocated.
Otherwise, it can return a false positive for a page that is not yet
resident because it is being read from disk.
between vm_map and vnode locks is that vm_map locks are acquired first. In
revision 1.150 mmap(2) was changed to pass a locked vnode into vm_mmap().
This creates a lock-order reversal when vm_mmap() calls one of the vm_map
routines that acquires a vm_map lock. The solution implemented herein is
to release the vnode lock in mmap() before calling vm_mmap() and reacquire
this lock if necessary in vm_mmap().
Approved by: re (scottl)
Reviewed by: jeff, kan, rwatson
1) mp_maxid is a valid FreeBSD CPU ID in the range 0 .. MAXCPU - 1.
2) For all active CPUs in the system, PCPU_GET(cpuid) <= mp_maxid.
Approved by: re (scottl)
Tested on: i386, amd64, alpha
was equal to MAXCPU, we would overrun the pcpu_mtx array because maxcpu
was calculated incorrectly.
- Add some more debugging code so that memory leaks at the time of
uma_zdestroy() are more easily diagnosed.
Approved by: re (rwatson)
occurs when kmem_malloc() fails to allocate a sufficient number of vm
pages. Specifically, we avoid the lock-order reversal by not grabbing
Giant around pmap_remove() if the map is the kmem_map.
Approved by: re (jhb)
Reported by: Eugene <eugene3@web.de>
on non-VCHR vnodes. This fixes a panic when reading data from files on a
filesystem with a small (less than a page) block size.
PR: 59271
Reviewed by: alc
- Return EBUSY if the region was wired by mlock(2) and MS_INVALIDATE
is specified to msync(2). This is required by the Open Group Base
Specifications Issue 6.
- vm_map_sync() doesn't return KERN_FAILURE. Thus, msync(2) can't
possibly return EIO.
- The second major loop in vm_map_sync() handles sub maps. Thus,
failing on sub maps in the first major loop isn't necessary.
must return EINVAL if size is zero. Submitted by: tegge
- In order to avoid a race condition in multithreaded applications, the
check and removal operations by munmap(2) must be in the same critical
section. To accomodate this, vm_map_check_protection() is modified to
require its caller to obtain at least a read lock on the map.
if we drop into the pmap or vnode layers.
- Migrate the handling of zero-length msync(2)s into vm_map_sync() so that
multithread applications can't change the map between implementing the
zero-length hack in msync(2) and reacquiring the map lock in
vm_map_sync().
Reviewed by: tegge
that msync(2) is its only caller.
- Migrate the parts of the old vm_map_clean() that examined the internals
of a vm object to a new function vm_object_sync() that is implemented in
vm_object.c. At the same, introduce the necessary vm object locking so
that vm_map_sync() and vm_object_sync() can be called without Giant.
Reviewed by: tegge
