tree is used to maintain the object's collection of resident pages,
vm_page_lookup() no longer needs an exclusive lock.
Reviewed by: attilio
Sponsored by: EMC / Isilon Storage Division
freelist.
o Split the pool of free pages queues really by domain and not rely on
definition of VM_RAW_NFREELIST.
o For MAXMEMDOM > 1, wrap the RR allocation logic into a specific
function that is called when calculating the allocation domain.
The RR counter is kept, currently, per-thread.
In the future it is expected that such function evolves in a real
policy decision referee, based on specific informations retrieved by
per-thread and per-vm_object attributes.
o Add the concept of "probed domains" under the form of vm_ndomains.
It is responsibility for every architecture willing to support multiple
memory domains to correctly probe vm_ndomains along with mem_affinity
segments attributes. Those two values are supposed to remain always
consistent.
Please also note that vm_ndomains and td_dom_rr_idx are both int
because segments already store domains as int. Ideally u_int would
have much more sense. Probabilly this should be cleaned up in the
future.
o Apply RR domain selection also to vm_phys_zero_pages_idle().
Sponsored by: EMC / Isilon storage division
Partly obtained from: jeff
Reviewed by: alc
Tested by: jeff
vm_page_insert() so that (1) vm_radix_lookup_le() is never called while the
free page queues lock is held and (2) vm_radix_lookup_le() is called at most
once. This change reduces the average time that the free page queues lock
is held by vm_page_alloc() as well as vm_page_alloc()'s average overall
running time.
Sponsored by: EMC / Isilon Storage Division
functions, reverse the numbering scheme for the levels. The highest
numbered level in the tree now appears near the root instead of the leaves.
Sponsored by: EMC / Isilon Storage Division
order to match the MAXCPU concept. The change should also be useful
for consolidation and consistency.
Sponsored by: EMC / Isilon storage division
Obtained from: jeff
Reviewed by: alc
change the way that these functions ascend the tree when the search for a
matching leaf fails at an interior node. Rather than returning to the root
of the tree and repeating the lookup with an updated key, maintain a stack
of interior nodes that were visited during the descent and use that stack
to resume the lookup at the closest ancestor that might have a matching
descendant.
Sponsored by: EMC / Isilon Storage Division
Reviewed by: attilio
Tested by: pho
- vm_phys_alloc_freelist_pages() can be called by vm_page_alloc_freelist()
to allocate a page from a specific freelist. In the NUMA case it did not
properly map the public VM_FREELIST_* constants to the correct backing
freelists, nor did it try all NUMA domains for allocations from
VM_FREELIST_DEFAULT.
- vm_phys_alloc_pages() did not pin the thread and each call to
vm_phys_alloc_freelist_pages() fetched the current domain to choose
which freelist to use. If a thread migrated domains during the loop
in vm_phys_alloc_pages() it could skip one of the freelists. If the
other freelists were out of memory then it is possible that
vm_phys_alloc_pages() would fail to allocate a page even though pages
were available resulting in a panic in vm_page_alloc().
Reviewed by: alc
MFC after: 1 week
vnode v_object to avoid double-buffering. Use the same object both as
the backing store for tmpfs node and as the v_object.
Besides reducing memory use up to 2x times for situation of mapping
files from tmpfs, it also makes tmpfs read and write operations copy
twice bytes less.
VM subsystem was already slightly adapted to tolerate OBJT_SWAP object
as v_object. Now the vm_object_deallocate() is modified to not
reinstantiate OBJ_ONEMAPPING flag and help the VFS to correctly handle
VV_TEXT flag on the last dereference of the tmpfs backing object.
Reviewed by: alc
Tested by: pho, bf
MFC after: 1 month
v_object of non OBJT_VNODE type.
For vm_object_page_clean(), simply do not assert that object type must
be OBJT_VNODE, and add a comment explaining how the check for
OBJ_MIGHTBEDIRTY prevents the rest of function from operating on such
objects.
For vm_mmap_vnode(), if the object type is not OBJT_VNODE, require it
to be for swap pager (or default), handle the bypass filesystems, and
correctly acquire the object reference in this case.
Reviewed by: alc
Tested by: pho, bf
MFC after: 1 week
to vnode_pager_setsize(), is either OBJT_VNODE, or, if vnode was
already reclaimed, OBJT_DEAD. Note that the later is only possible
due to some filesystems, in particular, nfsiods from nfs clients, call
vnode_pager_setsize() with unlocked vnode.
More, if the object is terminated, do not perform the resizing
operation.
Reviewed by: alc
Tested by: pho, bf
MFC after: 1 week
the number of interior nodes, we have previously created a level zero
interior node at the root of every non-empty trie, even when that node is
not strictly necessary, i.e., it has only one child. This change is the
second (and final) step in eliminating those unnecessary level zero interior
nodes. Specifically, it updates the deletion and insertion functions so
that they do not require a level zero interior node at the root of the trie.
For a "buildworld" workload, this change results in a 16.8% reduction in the
number of interior nodes allocated and a similar reduction in the average
execution time for lookup functions. For example, the average execution
time for a call to vm_radix_lookup_ge() is reduced by 22.9%.
Reviewed by: attilio, jeff (an earlier version)
Sponsored by: EMC / Isilon Storage Division
the number of interior nodes, we always create a level zero interior node at
the root of every non-empty trie, even when that node is not strictly
necessary, i.e., it has only one child. This change is the first step in
eliminating those unnecessary level zero interior nodes. Specifically, it
updates all of the lookup functions so that they do not require a level zero
interior node at the root.
Reviewed by: attilio, jeff (an earlier version)
Sponsored by: EMC / Isilon Storage Division
for us_freecount.
This grows uma_slab_head on 32-bit arches, but growth isn't
significant. Taking kmem zones as example, only the 32 byte
zone is affected, ipers is reduced from 113 to 112.
In collaboration with: kib
with the MAP_ENTRY_VN_WRITECNT flag:
- Move the assertion that verifies the state of the v_writecount and
vnp.writecount, under the block where the object is locked.
- Check that the object type is OBJT_VNODE before asserting.
Reported by: avg
Reviewed by: alc
MFC after: 1 week
per-page lock rather than vm_object lock, without any further overhead.
Make the formal switch.
Sponsored by: EMC / Isilon storage division
Reviewed by: alc
Tested by: pho
These zones have slab size == sizeof(struct pcpu), but request from VM
enough pages to fit (uk_slabsize * mp_ncpus). An item allocated from such
zone would have a separate twin for each CPU in the system, and these twins
are at a distance of sizeof(struct pcpu) from each other. This magic value
of distance would allow us to make some optimizations later.
To address private item from a CPU simple arithmetics should be used:
item = (type *)((char *)base + sizeof(struct pcpu) * curcpu)
These arithmetics are available as zpcpu_get() macro in pcpu.h.
To introduce non-page size slabs a new field had been added to uma_keg
uk_slabsize. This shifted some frequently used fields of uma_keg to the
fourth cache line on amd64. To mitigate this pessimization, uma_keg fields
were a bit rearranged and least frequently used uk_name and uk_link moved
down to the fourth cache line. All other fields, that are dereferenced
frequently fit into first three cache lines.
Sponsored by: Nginx, Inc.
arrange for all of the fields to start at a short offset from the
beginning of the structure.
Eliminate unnecessary masking of VM_RADIX_FLAGS from the root pointer in
vm_radix_getroot().
Sponsored by: EMC / Isilon Storage Division
- Don't insert BKGRDMARKER bufs into the splay or dirty/clean buf lists.
No consumers need to find them there and it complicates the tree.
These flags are all FFS specific and could be moved out of the buf
cache.
- Use pbgetvp() and pbrelvp() to associate the background and journal
bufs with the vp. Not only is this much cheaper it makes more sense
for these transient bufs.
- Fix the assertions in pbget* and pbrel*. It's not safe to check list
pointers which were never initialized. Use the BX flags instead. We
also check B_PAGING in reassignbuf() so this should cover all cases.
Discussed with: kib, mckusick, attilio
Sponsored by: EMC / Isilon Storage Division
vm_radix_topage(). This transformation eliminates some unnecessary
conditional branches from the inner loops of vm_radix_insert(),
vm_radix_lookup{,_ge,_le}(), and vm_radix_remove().
Simplify the control flow of vm_radix_lookup_{ge,le}().
Reviewed by: attilio (an earlier version)
Tested by: pho
Sponsored by: EMC / Isilon Storage Division
before the vnode is vput() in vm_mmap_vnode(). Error return means
that there is no use reference on the vnode from the vm object
reference, and failing to restore v_writecount breaks the invariant
that v_writecount is less or equal to the usecount.
The situation observed when nfs client returns ESTALE for
VOP_GETATTR() after the open.
In collaboration with: pho
MFC after: 1 week
using vm_radix_node_page() == NULL, the compiler is able to generate one
less conditional branch when vm_radix_isleaf() is used. More use cases
involving the inner loops of vm_radix_insert(), vm_radix_lookup{,_ge,_le}(),
and vm_radix_remove() will follow.
Reviewed by: attilio
Sponsored by: EMC / Isilon Storage Division
that could never be reached in vm_radix_insert(). (If the pointer being
checked by the panic call were ever NULL, the immmediately preceding loop
would have already crashed on a NULL pointer dereference.)
Reviewed by: attilio (an earlier version)
Sponsored by: EMC / Isilon Storage Division
do not map the b_pages pages into buffer_map KVA. The use of the
unmapped buffers eliminate the need to perform TLB shootdown for
mapping on the buffer creation and reuse, greatly reducing the amount
of IPIs for shootdown on big-SMP machines and eliminating up to 25-30%
of the system time on i/o intensive workloads.
The unmapped buffer should be explicitely requested by the GB_UNMAPPED
flag by the consumer. For unmapped buffer, no KVA reservation is
performed at all. The consumer might request unmapped buffer which
does have a KVA reserve, to manually map it without recursing into
buffer cache and blocking, with the GB_KVAALLOC flag.
When the mapped buffer is requested and unmapped buffer already
exists, the cache performs an upgrade, possibly reusing the KVA
reservation.
Unmapped buffer is translated into unmapped bio in g_vfs_strategy().
Unmapped bio carry a pointer to the vm_page_t array, offset and length
instead of the data pointer. The provider which processes the bio
should explicitely specify a readiness to accept unmapped bio,
otherwise g_down geom thread performs the transient upgrade of the bio
request by mapping the pages into the new bio_transient_map KVA
submap.
The bio_transient_map submap claims up to 10% of the buffer map, and
the total buffer_map + bio_transient_map KVA usage stays the
same. Still, it could be manually tuned by kern.bio_transient_maxcnt
tunable, in the units of the transient mappings. Eventually, the
bio_transient_map could be removed after all geom classes and drivers
can accept unmapped i/o requests.
Unmapped support can be turned off by the vfs.unmapped_buf_allowed
tunable, disabling which makes the buffer (or cluster) creation
requests to ignore GB_UNMAPPED and GB_KVAALLOC flags. Unmapped
buffers are only enabled by default on the architectures where
pmap_copy_page() was implemented and tested.
In the rework, filesystem metadata is not the subject to maxbufspace
limit anymore. Since the metadata buffers are always mapped, the
buffers still have to fit into the buffer map, which provides a
reasonable (but practically unreachable) upper bound on it. The
non-metadata buffer allocations, both mapped and unmapped, is
accounted against maxbufspace, as before. Effectively, this means that
the maxbufspace is forced on mapped and unmapped buffers separately.
The pre-patch bufspace limiting code did not worked, because
buffer_map fragmentation does not allow the limit to be reached.
By Jeff Roberson request, the getnewbuf() function was split into
smaller single-purpose functions.
Sponsored by: The FreeBSD Foundation
Discussed with: jeff (previous version)
Tested by: pho, scottl (previous version), jhb, bf
MFC after: 2 weeks
Replace the per-object resident and cached pages splay tree with a
path-compressed multi-digit radix trie.
Along with this, switch also the x86-specific handling of idle page
tables to using the radix trie.
This change is supposed to do the following:
- Allowing the acquisition of read locking for lookup operations of the
resident/cached pages collections as the per-vm_page_t splay iterators
are now removed.
- Increase the scalability of the operations on the page collections.
The radix trie does rely on the consumers locking to ensure atomicity of
its operations. In order to avoid deadlocks the bisection nodes are
pre-allocated in the UMA zone. This can be done safely because the
algorithm needs at maximum one new node per insert which means the
maximum number of the desired nodes is the number of available physical
frames themselves. However, not all the times a new bisection node is
really needed.
The radix trie implements path-compression because UFS indirect blocks
can lead to several objects with a very sparse trie, increasing the number
of levels to usually scan. It also helps in the nodes pre-fetching by
introducing the single node per-insert property.
This code is not generalized (yet) because of the possible loss of
performance by having much of the sizes in play configurable.
However, efforts to make this code more general and then reusable in
further different consumers might be really done.
The only KPI change is the removal of the function vm_page_splay() which
is now reaped.
The only KBI change, instead, is the removal of the left/right iterators
from struct vm_page, which are now reaped.
Further technical notes broken into mealpieces can be retrieved from the
svn branch:
http://svn.freebsd.org/base/user/attilio/vmcontention/
Sponsored by: EMC / Isilon storage division
In collaboration with: alc, jeff
Tested by: flo, pho, jhb, davide
Tested by: ian (arm)
Tested by: andreast (powerpc)
pages around, taking array of vm_page_t both for source and
destination. Starting offsets and total transfer size are specified.
The function implements optimal algorithm for copying using the
platform-specific optimizations. For instance, on the architectures
were the direct map is available, no transient mappings are created,
for i386 the per-cpu ephemeral page frame is used. The code was
typically borrowed from the pmap_copy_page() for the same
architecture.
Only i386/amd64, powerpc aim and arm/arm-v6 implementations were
tested at the time of commit. High-level code, not committed yet to
the tree, ensures that the use of the function is only allowed after
explicit enablement.
For sparc64, the existing code has known issues and a stab is added
instead, to allow the kernel linking.
Sponsored by: The FreeBSD Foundation
Tested by: pho (i386, amd64), scottl (amd64), ian (arm and arm-v6)
MFC after: 2 weeks
future further optimizations where the vm_object lock will be held
in read mode most of the time the page cache resident pool of pages
are accessed for reading purposes.
The change is mostly mechanical but few notes are reported:
* The KPI changes as follow:
- VM_OBJECT_LOCK() -> VM_OBJECT_WLOCK()
- VM_OBJECT_TRYLOCK() -> VM_OBJECT_TRYWLOCK()
- VM_OBJECT_UNLOCK() -> VM_OBJECT_WUNLOCK()
- VM_OBJECT_LOCK_ASSERT(MA_OWNED) -> VM_OBJECT_ASSERT_WLOCKED()
(in order to avoid visibility of implementation details)
- The read-mode operations are added:
VM_OBJECT_RLOCK(), VM_OBJECT_TRYRLOCK(), VM_OBJECT_RUNLOCK(),
VM_OBJECT_ASSERT_RLOCKED(), VM_OBJECT_ASSERT_LOCKED()
* The vm/vm_pager.h namespace pollution avoidance (forcing requiring
sys/mutex.h in consumers directly to cater its inlining functions
using VM_OBJECT_LOCK()) imposes that all the vm/vm_pager.h
consumers now must include also sys/rwlock.h.
* zfs requires a quite convoluted fix to include FreeBSD rwlocks into
the compat layer because the name clash between FreeBSD and solaris
versions must be avoided.
At this purpose zfs redefines the vm_object locking functions
directly, isolating the FreeBSD components in specific compat stubs.
The KPI results heavilly broken by this commit. Thirdy part ports must
be updated accordingly (I can think off-hand of VirtualBox, for example).
Sponsored by: EMC / Isilon storage division
Reviewed by: jeff
Reviewed by: pjd (ZFS specific review)
Discussed with: alc
Tested by: pho
