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
be eliminated. If the calls to vm_radix_lookup_le() return NULL, then
the page at the head of the object's memq must be the page with the least
pindex greater than the specified pindex.
Reviewed by: attilio
Sponsored by: EMC / Isilon Storage Division
vm_radix_node_get() with a small change to vm_radix_reclaim_allnodes_int().
This change further reduced the average number of cycles per
vm_page_insert() call from 532 to 519.
Reviewed by: attilio
Sponsored by: EMC / Isilon Storage Division
indices. Consequentially, vm_page_insert() should use
vm_radix_lookup_le() instead of vm_radix_lookup_ge(). Here's why. In
the expected case, vm_radix_lookup_le() will quickly find a page less
than the specified key at the same radix node. In contrast,
vm_radix_lookup_ge() is expected to return NULL, but to do that it must
examine every slot in the radix tree that is greater than the key.
Prior to this change, the average cost of a vm_page_insert() call on my
test machine was 992 cycles. After this change, the average cost is only
532 cycles, a reduction of 46%.
Reviewed by: attilio
Sponsored by: EMC / Isilon Storage Division
"index". The content of a radix tree leaf, or at least its "key", is not
opaque to the other radix tree operations. Specifically, they know how to
extract the "key" from a leaf. So, eliminating the parameter "index" isn't
breaking the abstraction. Moreover, eliminating the parameter "index"
effectively prevents the caller from passing an inconsistent "index" and
leaf to vm_radix_insert().
Reviewed by: attilio
Sponsored by: EMC / Isilon Storage Division
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
page into its new object until the page's pindex has been updated.
Otherwise, one code path within vm_radix_insert() may use the wrong
pindex value.
Sponsored by: EMC / Isilon Storage Division
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
Introduce a new KPI that verifies if the page cache is empty for a
specified vm_object. This KPI does not make assumptions about the
locking in order to be used also for building assertions at init and
destroy time.
It is mostly used to hide implementation details of the page cache.
Sponsored by: EMC / Isilon storage division
Reviewed by: jeff
Reviewed by: alc (vm_radix based version)
Tested by: flo, pho, jhb, davide
