excluding other allocations including UMA now entails the addition of
a single flag to kmem_alloc or uma zone create
Reviewed by: alc, avg
MFC after: 2 weeks
yielding a new public interface, vm_page_alloc_contig(). This new function
addresses some of the limitations of the current interfaces, contigmalloc()
and kmem_alloc_contig(). For example, the physically contiguous memory that
is allocated with those interfaces can only be allocated to the kernel vm
object and must be mapped into the kernel virtual address space. It also
provides functionality that vm_phys_alloc_contig() doesn't, such as wiring
the returned pages. Moreover, unlike that function, it respects the low
water marks on the paging queues and wakes up the page daemon when
necessary. That said, at present, this new function can't be applied to all
types of vm objects. However, that restriction will be eliminated in the
coming weeks.
From a design standpoint, this change also addresses an inconsistency
between vm_phys_alloc_contig() and the other vm_phys_alloc*() functions.
Specifically, vm_phys_alloc_contig() manipulated vm_page fields that other
functions in vm/vm_phys.c didn't. Moreover, vm_phys_alloc_contig() knew
about vnodes and reservations. Now, vm_page_alloc_contig() is responsible
for these things.
Reviewed by: kib
Discussed with: jhb
eliminating duplicated code in the various pmap implementations.
Micro-optimize vm_phys_free_pages().
Introduce vm_phys_free_contig(). It is fast routine for freeing an
arbitrary number of physically contiguous pages. In particular, it
doesn't require the number of pages to be a power of two.
Use "u_long" instead of "unsigned long".
Bruce Evans (bde@) has convinced me that the "boundary" parameters
to kmem_alloc_contig(), vm_phys_alloc_contig(), and
vm_reserv_reclaim_contig() should be of type "vm_paddr_t" and not
"u_long". Make this change.
more general VM system interfaces. So, their implementation can now
reside in kern_malloc.c alongside the other functions that are declared
in malloc.h.
instead skip over them. As long as a page is held, it can't be reclaimed by
contigmalloc(M_WAITOK). Moreover, a held page may be undergoing
modification, e.g., vmapbuf(), so even if the hold were released before the
completion of contigmalloc(), the page might have to be flushed again.
MFC after: 3 weeks
backing storage. Such pages might be then reused, racing with the
assert in vm_object_page_collect_flush() that verified that dirty
pages from the run (most likely, pages with VM_PAGER_AGAIN status) are
write-protected still. In fact, the page indexes for the pages that
were removed from the object page list should be ignored by
vm_object_page_clean().
Return the length of successfully written run from vm_pageout_flush(),
that is, the count of pages between requested page and first page
after requested with status VM_PAGER_AGAIN. Supply the requested page
index in the array to vm_pageout_flush(). Use the returned run length
to forward the index of next page to clean in vm_object_page_clean().
Reported by: avg
Reviewed by: alc
MFC after: 1 week
fails to allocate MIPS page table pages. The current usage of VM_WAIT in
case of vm_phys_alloc_contig() failure is not correct, because:
"There is no guarantee that any of the available free (or cached) pages
after the VM_WAIT will fall within the range of suitable physical
addresses. Every time this function sleeps and a single page is freed
(or cached) by someone else, this function will be reawakened. With
a little bad luck, you could spin indefinitely."
We also add low and high parameters to vm_contig_grow_cache() and
vm_contig_launder() so that we restrict vm_contig_launder() to the range
of pages we are interested in.
Reported by: alc
Reviewed by: alc
Approved by: rrs (mentor)
vm_pageout_fallback_object_lock(), to obtain the page lock
while having page queue lock locked, and still maintain the
page position in a queue.
Use the helper to lock the page in the pageout daemon and contig launder
iterators instead of skipping the page if its lock is contested.
Skipping locked pages easily causes pagedaemon or launder to not make a
progress with page cleaning.
Proposed and reviewed by: alc
revision, r207450, to this file. Specifically, between dropping the page
queues lock in vm_contig_launder() and reacquiring it in
vm_contig_launder_page(), the page may be removed from the active or
inactive queue. It could be wired, freed, cached, etc. None of which
vm_contig_launder_page() is prepared for.
Reviewed by: kib, kmacy
architecture from page queue lock to a hashed array of page locks
(based on a patch by Jeff Roberson), I've implemented page lock
support in the MI code and have only moved vm_page's hold_count
out from under page queue mutex to page lock. This changes
pmap_extract_and_hold on all pmaps.
Supported by: Bitgravity Inc.
Discussed with: alc, jeffr, and kib
memory with the specified physical attributes. In particular, like
kmem_alloc_contig(), the caller can specify the physical address range
from which the physical pages are allocated and the memory attributes
(i.e., cache behavior) for these physical pages. However, in contrast to
kmem_alloc_contig() or contigmalloc(), the physical pages that are
allocated by kmem_alloc_attr() are not necessarily physically contiguous.
This function is needed by DRM and VirtualBox.
Correct an error in the prototype for kmem_malloc(). The third argument
had the wrong type.
Tested by: rnoland
MFC after: 3 days
dependent memory attributes:
Rename vm_cache_mode_t to vm_memattr_t. The new name reflects the
fact that there are machine-dependent memory attributes that have
nothing to do with controlling the cache's behavior.
Introduce vm_object_set_memattr() for setting the default memory
attributes that will be given to an object's pages.
Introduce and use pmap_page_{get,set}_memattr() for getting and
setting a page's machine-dependent memory attributes. Add full
support for these functions on amd64 and i386 and stubs for them on
the other architectures. The function pmap_page_set_memattr() is also
responsible for any other machine-dependent aspects of changing a
page's memory attributes, such as flushing the cache or updating the
direct map. The uses include kmem_alloc_contig(), vm_page_alloc(),
and the device pager:
kmem_alloc_contig() can now be used to allocate kernel memory with
non-default memory attributes on amd64 and i386.
vm_page_alloc() and the device pager will set the memory attributes
for the real or fictitious page according to the object's default
memory attributes.
Update the various pmap functions on amd64 and i386 that map pages to
incorporate each page's memory attributes in the mapping.
Notes: (1) Inherent to this design are safety features that prevent
the specification of inconsistent memory attributes by different
mappings on amd64 and i386. In addition, the device pager provides a
warning when a device driver creates a fictitious page with memory
attributes that are inconsistent with the real page that the
fictitious page is an alias for. (2) Storing the machine-dependent
memory attributes for amd64 and i386 as a dedicated "int" in "struct
md_page" represents a compromise between space efficiency and the ease
of MFCing these changes to RELENG_7.
In collaboration with: jhb
Approved by: re (kib)
required by video card drivers. Specifically, this change introduces
vm_cache_mode_t with an appropriate VM_CACHE_DEFAULT definition on all
architectures. In addition, this changes adds a vm_cache_mode_t parameter
to kmem_alloc_contig() and vm_phys_alloc_contig(). These will be the
interfaces for allocating mapped kernel memory and physical memory,
respectively, with non-default cache modes.
In collaboration with: jhb
with the malloc tag and calls a new back-end, kmem_alloc_contig(), that
allocates the pages and maps them.
The motivations for this change are two-fold: (1) A cache mode parameter
will be added to kmem_alloc_contig(). In other words, kmem_alloc_contig()
will be extended to support the allocation of memory with caller-specified
caching. (2) The UMA allocation function that is used by the two jumbo
frames zones can use kmem_alloc_contig() in place of contigmalloc() and
thereby avoid having free jumbo frames held by the zone counted as live
malloc()ed memory.
kmem_alloc() and kmem_malloc(). Specifically, defer the setting of the
page's valid bits until contigmapping() when the mapping is known to be
successful.
conjuction with 'thread' argument passing which is always curthread.
Remove the unuseful extra-argument and pass explicitly curthread to lower
layer functions, when necessary.
KPI results broken by this change, which should affect several ports, so
version bumping and manpage update will be further committed.
Tested by: kris, pho, Diego Sardina <siarodx at gmail dot com>
Remove this argument and pass curthread directly to underlying
VOP_LOCK1() VFS method. This modify makes the code cleaner and in
particular remove an annoying dependence helping next lockmgr() cleanup.
KPI results, obviously, changed.
Manpage and FreeBSD_version will be updated through further commits.
As a side note, would be valuable to say that next commits will address
a similar cleanup about VFS methods, in particular vop_lock1 and
vop_unlock.
Tested by: Diego Sardina <siarodx at gmail dot com>,
Andrea Di Pasquale <whyx dot it at gmail dot com>
vm_pageout_fallback_object_lock() in vm_contig_launder_page() to better
handle a lock-ordering problem. Consequently, trylock's failure on the
page's containing object no longer implies that the page cannot be
laundered.
MFC after: 6 weeks
malloc_type_allocated(..., 0) calls that occur when contigmalloc() has
failed. Eliminate the acquisition and release of the page queues lock
from vm_page_release_contig(). Rename contigmalloc2() to
contigmapping(), reflecting what it does.
ways:
(1) Cached pages are no longer kept in the object's resident page
splay tree and memq. Instead, they are kept in a separate per-object
splay tree of cached pages. However, access to this new per-object
splay tree is synchronized by the _free_ page queues lock, not to be
confused with the heavily contended page queues lock. Consequently, a
cached page can be reclaimed by vm_page_alloc(9) without acquiring the
object's lock or the page queues lock.
This solves a problem independently reported by tegge@ and Isilon.
Specifically, they observed the page daemon consuming a great deal of
CPU time because of pages bouncing back and forth between the cache
queue (PQ_CACHE) and the inactive queue (PQ_INACTIVE). The source of
this problem turned out to be a deadlock avoidance strategy employed
when selecting a cached page to reclaim in vm_page_select_cache().
However, the root cause was really that reclaiming a cached page
required the acquisition of an object lock while the page queues lock
was already held. Thus, this change addresses the problem at its
root, by eliminating the need to acquire the object's lock.
Moreover, keeping cached pages in the object's primary splay tree and
memq was, in effect, optimizing for the uncommon case. Cached pages
are reclaimed far, far more often than they are reactivated. Instead,
this change makes reclamation cheaper, especially in terms of
synchronization overhead, and reactivation more expensive, because
reactivated pages will have to be reentered into the object's primary
splay tree and memq.
(2) Cached pages are now stored alongside free pages in the physical
memory allocator's buddy queues, increasing the likelihood that large
allocations of contiguous physical memory (i.e., superpages) will
succeed.
Finally, as a result of this change long-standing restrictions on when
and where a cached page can be reclaimed and returned by
vm_page_alloc(9) are eliminated. Specifically, calls to
vm_page_alloc(9) specifying VM_ALLOC_INTERRUPT can now reclaim and
return a formerly cached page. Consequently, a call to malloc(9)
specifying M_NOWAIT is less likely to fail.
Discussed with: many over the course of the summer, including jeff@,
Justin Husted @ Isilon, peter@, tegge@
Tested by: an earlier version by kris@
Approved by: re (kensmith)
This allocator uses a binary buddy system with a twist. First and
foremost, this allocator is required to support the implementation of
superpages. As a side effect, it enables a more robust implementation
of contigmalloc(9). Moreover, this reimplementation of
contigmalloc(9) eliminates the acquisition of Giant by
contigmalloc(..., M_NOWAIT, ...).
The twist is that this allocator tries to reduce the number of TLB
misses incurred by accesses through a direct map to small, UMA-managed
objects and page table pages. Roughly speaking, the physical pages
that are allocated for such purposes are clustered together in the
physical address space. The performance benefits vary. In the most
extreme case, a uniprocessor kernel running on an Opteron, I measured
an 18% reduction in system time during a buildworld.
This allocator does not implement page coloring. The reason is that
superpages have much the same effect. The contiguous physical memory
allocation necessary for a superpage is inherently colored.
Finally, the one caveat is that this allocator does not effectively
support prezeroed pages. I hope this is temporary. On i386, this is
a slight pessimization. However, on amd64, the beneficial effects of
the direct-map optimization outweigh the ill effects. I speculate
that this is true in general of machines with a direct map.
Approved by: re
Probabilly, a general approach is not the better solution here, so we should
solve the sched_lock protection problems separately.
Requested by: alc
Approved by: jeff (mentor)
vmcnts. This can be used to abstract away pcpu details but also changes
to use atomics for all counters now. This means sched lock is no longer
responsible for protecting counts in the switch routines.
Contributed by: Attilio Rao <attilio@FreeBSD.org>
contigmalloc2() was always testing the first physical page for PG_ZERO,
not the current page of interest.
Submitted by: Michael Plass
PR: 81301
MFC after: 1 week
size aligned requiring heavy usage of vm_page_alloc_contig
This change makes vm_page_alloc_contig SMP safe
Approved by: scottl (acting as backup for mentor rwatson)
be called without any vnode locks held. Remove calls to vn_start_write() and
vn_finished_write() in vnode_pager_putpages() and add these calls before the
vnode lock is obtained to most of the callers that don't already have them.
of physical RAM instead of the bottom was a sound idea, but the implementation
left a lot to be desired. Scans would spend considerable time looking at
pages that are above of the address range given by the caller, and multiple
calls (like what happens in busdma) would spend more time on top of that
rescanning the same pages over and over.
Solve this, at least for now, with two simple optimizations. The first is
to not bother scanning high ordered pages that are outside of the provided
address range. Second is to cache the page index from the last successful
operation so that subsequent scans don't have to restart from the top. This
is conditional on the numpages argument being the same or greater between
calls.
MFC After: 2 weeks
statement. Specifically, a break statement that previously broke out of
the enclosing switch was not changed. Consequently, the enclosing loop
terminated prematurely.
This could result in "vm_page_insert: page already inserted" panics.
Submitted by: tegge
