This KASSERT is overzealous because of the following race condition:
1) A managed page which is currently in PQ_LAUNDRY is freed.
vm_page_free_prep calls vm_page_dequeue_deferred()
The page state is:
PQ_LAUNDRY, PGA_DEQUEUE|PGA_ENQUEUED
2) The laundry worker comes around and pick up the page and calls
vm_pageout_defer(m, PQ_LAUNDRY, true) to check if page is still in the
queue. We do a vm_page_astate_load and get
PQ_LAUNDRY, PGA_DEQUEUE|PGA_ENQUEUED
as per above.
3) The laundry worker is pre-empted and another thread allocates our page
from the free pool. For example vm_page_alloc_domain_after calls
vm_page_dequeue() and sets VPO_UNMANAGED because we are allocating for
an OBJT_UNMANAGED object.
The page state is:
PQ_NONE, 0 - VPO_UNMANAGED
4) The laundry worker resumes, and processes vm_pageout_defer based on the
stale astate which leads to a call to vm_page_pqbatch_submit, which will
trip on the KASSERT.
Submitted by: mlaier
Reviewed by: markj, rlibby
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D28563
Otherwise, on a powerpc64 NUMA system with hashed page tables, the
first-level superpage reservation size is large enough that the value of
the kernel KVA arena import quantum, KVA_NUMA_IMPORT_QUANTUM, is
negative and gets sign-extended when passed to vmem_set_import(). This
results in a boot-time hang on such platforms.
Reported by: bdragon
MFC after: 3 days
KCSAN complains about racy accesses in the locking code. Those races are
fine since they are inside a TD_SET_RUNNING() loop that expects the value
to be changed by another CPU.
Use relaxed atomic stores/loads to indicate that this variable can be
written/read by multiple CPUs at the same time. This will also prevent
the compiler from doing unexpected re-ordering.
Reported by: GENERIC-KCSAN
Test Plan: KCSAN no longer complains, kernel still runs fine.
Reviewed By: markj, mjg (earlier version)
Differential Revision: https://reviews.freebsd.org/D28569
This macro returns true if a provided virtual address is contained
in the kernel's clean submap.
In CHERI kernels, the buffer cache and transient I/O map are allocated
as separate regions. Abstracting this check reduces the diff relative
to FreeBSD. It is perhaps slightly more readable as well.
Reviewed by: kib
Obtained from: CheriBSD
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D28710
This flag indicates that the page should be enqueued near the head of
the inactive queue, skipping the LRU queue. It is used when unwiring
pages from the buffer cache following direct I/O or after I/O when
POSIX_FADV_NOREUSE or _DONTNEED advice was specified, or when
sendfile(SF_NOCACHE) completes. For the direct I/O and sendfile cases
we only enqueue the page if we decide not to free it, typically because
it's mapped.
Pass "noreuse" through to vm_page_release_toq() so that we actually
honour the desired LRU policy for these scenarios.
Reported by: bdrewery
Reviewed by: alc, kib
MFC after: 3 days
Differential Revision: https://reviews.freebsd.org/D28555
If a M_WAITOK contig alloc fails, the VM subsystem will try to
reclaim contiguous memory twice before actually failing the
request. On a system with 64GB of RAM I've observed this take
400-500ms before it finally gives up, and I believe that this
will only be worse on systems with even more memory.
In certain contexts this delay is extremely harmful, so add a flag
that will skip reclaim for allocation requests to allow those
paths to opt-out of doing an expensive reclaim.
Sponsored by: Dell Inc
Differential Revision: https://reviews.freebsd.org/D28422
Reviewed by: markj, kib
Replace all uses of kern_mmap with kern_mmap_req move the old kern_mmap.
Reand rename kern_mmap_req to kern_mmap .
The helper saved some code churn initially, but having multiple
interfaces is sub-optimal.
Obtained from: CheriBSD
Reviewed by: kib
Differential Revision: https://reviews.freebsd.org/D28292
This prevents a situation where other thread modifies map entries
permissions between setting max_prot, then relocking, then setting prot,
confusing the operation outcome. E.g. you can get an error that is not
possible if operation is performed atomic.
Also enable setting rwx for max_prot even if map does not allow to set
effective rwx protection.
Reviewed by: brooks, markj (previous version)
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D28117
It is checked in vm_map_insert() and vm_map_protect() that PROT_WRITE |
PROT_EXEC are never specified together, if vm_map has MAP_WX flag set.
FreeBSD control flag allows specific binary to request WX exempt, and
there are per ABI boolean sysctls kern.elf{32,64}.allow_wx to enable/
disable globally.
Reviewed by: emaste, jhb
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D28050
startup_alloc() uses pmap_map() to map slabs used for bootstrapping the
VM. pmap_map() may ignore the hint address and simply return a range
from the direct map. In this case we must not unmap the range in
startup_free().
UMA uses bootstart and bootmem to track the range of KVA into which
slabs are mapped if the direct map is not used. Unmap a startup slab
only if it was mapped into that range.
Reported by: alc
Reviewed by: alc, kib
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D27885
Use atomic testandset and testandclear to catch concurrent double free,
and to reduce the number of atomic operations.
Submitted by: jeff
Reviewed by: cem, kib, markj (all previous version)
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D22703
In vm_page_busy_acquire(), load the object pointer using
atomic_load_ptr() as we do elsewhere. Per the comment, the object
identity must be consistent across sleeps.
In vm_page_grab_sleep(), pass the correct pindex to
_vm_page_busy_sleep(). The pindex is used to re-check the page's
identity before going to sleep. In particular, vm_page_grab_sleep() is
used in unlocked grab, so the object lock is not necessarily held when
verifying the page's identity, and the pindex may change if the page is
moved, or freed and re-allocated. I believe this can result in spurious
VM_PAGER_FAILs from vm_page_grab_valid_unlocked() or early termination
of vm_page_grab_pages_unlocked().
In vm_page_grab_pages(), pass the correct pindex to
vm_page_grab_sleep(). Otherwise I believe vm_page_grab_pages() will
effectively spin when attempting to busy a busy page after the first
index in the range.
Reviewed by: alc, kib
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D27607
This restores behavior from before domain iterators were added in
r327895 and r327896.
The vm_domainset_iter_policy() will do a vm_wait_doms() and then
restart its iterator when M_WAITOK is set. It will also force
the containing loop to have M_NOWAIT. So we get an unbounded
retry loop rather than the intended bounded retries that
kmem_alloc_contig_pages() already handles.
This also restores M_WAITOK to the vmem_alloc() call in
kmem_alloc_attr_domain() and kmem_alloc_contig_domain().
Reviewed by: markj, kib
MFC after: 2 weeks
Sponsored by: Dell EMC
Differential Revision: https://reviews.freebsd.org/D27507
The old implementation chose the largest bucket zone such that if the
per-CPU caches are fully populated, the total number of items cached is
no larger than the specified limit. If no such zone existed, UMA would
not do any caching.
We can now use uz_bucket_size_max to set a precise limit on the number
of items in a zone's bucket, so the total size of per-CPU caches can be
bounded more easily. Implement a new policy in uma_zone_set_maxcache():
choose a bucket size such that up to half of the limit can be cached in
per-CPU caches, with the rest going to the full bucket cache. This
fixes a problem with the kstack_cache zone: the limit of 4 * mp_ncpus
items meant that the zone would not do any caching, defeating the whole
purpose of the zone. That's because the smallest bucket size holds up
to 2 items and we may cache up to 3 full buckets per CPU, and
2 * 3 * mp_ncpus > 4 * mp_ncpus.
Reported by: mjg
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D27168
uz_bucket_size_max is the maximum permitted bucket size. When filling a
new bucket to satisfy uma_zalloc(), the bucket is populated with at most
uz_bucket_size_max items. The maximum number of entries in the bucket
may be larger. When freeing items, however, we will fill per-CPPU
buckets up to their maximum number of entries, potentially exceeding
uz_bucket_size_max. This makes it difficult to precisely limit the
number of items that may be cached in a zone. For example, if one wants
to limit buckets to 1 entry for a particular zone, that's not possible
since the smallest bucket holds up to 2 entries.
Try to solve the problem by using uz_bucket_size_max to limit the number
of entries in a bucket. Note that the ub_entries field is initialized
upon every bucket allocation. Most zones are not affected since they do
not impose any specific limit on the maximum bucket size.
While here, remove the UMA_ZONE_MINBUCKET flag. It was unused and we
now have uma_zone_set_maxcache() to control the zone's cache size more
precisely.
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D27167
Allocation of a bucket can trigger a cross-domain free in the bucket
zone, e.g., if the per-CPU alloc bucket is empty, we free it and get
migrated to a remote domain. This can lead to deadlocks since a bucket
zone may allocate buckets from itself or a pair of bucket zones could be
allocating from each other.
Fix the problem by dropping the cross-domain lock before allocating a
new bucket and handling refill races. Use a list of empty buckets to
ensure that we can make forward progress.
Reported by: imp, mjg (witness(9) warnings)
Discussed with: jeff
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D27341
Replace MAXPHYS by runtime variable maxphys. It is initialized from
MAXPHYS by default, but can be also adjusted with the tunable kern.maxphys.
Make b_pages[] array in struct buf flexible. Size b_pages[] for buffer
cache buffers exactly to atop(maxbcachebuf) (currently it is sized to
atop(MAXPHYS)), and b_pages[] for pbufs is sized to atop(maxphys) + 1.
The +1 for pbufs allow several pbuf consumers, among them vmapbuf(),
to use unaligned buffers still sized to maxphys, esp. when such
buffers come from userspace (*). Overall, we save significant amount
of otherwise wasted memory in b_pages[] for buffer cache buffers,
while bumping MAXPHYS to desired high value.
Eliminate all direct uses of the MAXPHYS constant in kernel and driver
sources, except a place which initialize maxphys. Some random (and
arguably weird) uses of MAXPHYS, e.g. in linuxolator, are converted
straight. Some drivers, which use MAXPHYS to size embeded structures,
get private MAXPHYS-like constant; their convertion is out of scope
for this work.
Changes to cam/, dev/ahci, dev/ata, dev/mpr, dev/mpt, dev/mvs,
dev/siis, where either submitted by, or based on changes by mav.
Suggested by: mav (*)
Reviewed by: imp, mav, imp, mckusick, scottl (intermediate versions)
Tested by: pho
Sponsored by: The FreeBSD Foundation
Differential revision: https://reviews.freebsd.org/D27225
It can useful for code outside the VM system to look up the NUMA domain
of a page backing a virtual or physical address, specifically when
creating NUMA-aware data structures. We have _vm_phys_domain() for
this, but the leading underscore implies that it's an internal function,
and vm_phys.h has dependencies on a number of other headers.
Rename vm_phys_domain() to vm_page_domain(), and _vm_phys_domain() to
vm_phys_domain(). Make the latter an inline function.
Add _vm_phys.h and define struct vm_phys_seg there so that it's easier
to use in other headers. Include it from vm_page.h so that
vm_page_domain() can be defined there.
Include machine/vmparam.h from _vm_phys.h since it depends directly on
some constants defined there.
Reviewed by: alc
Reviewed by: dougm, kib (earlier versions)
Differential Revision: https://reviews.freebsd.org/D27207
On platforms without a direct map[*], vm_map_insert() may in rare
situations need to allocate a kernel map entry in order to allocate
kernel map entries. This poses a problem similar to the one solved for
vmem boundary tags by vmem_bt_alloc(). In fact the kernel map case is a
bit more complicated since we must allocate entries with the kernel map
locked, whereas vmem can recurse into itself because boundary tags are
allocated up-front.
The solution is to add a custom slab allocator for kmapentzone which
allocates KVA directly from kernel_map, bypassing the kmem_* layer.
This avoids mutual recursion with the vmem btag allocator. Then, when
vm_map_insert() allocates a new kernel map entry, it avoids triggering
allocation of a new slab with M_NOVM until after the insertion is
complete. Instead, vm_map_insert() allocates from the reserve and sets
a flag in kernel_map to trigger re-population of the reserve just before
the map is unlocked. This places an implicit upper bound on the number
of kernel map entries that may be allocated before the kernel map lock
is released, but in general a bound of 1 suffices.
[*] This also comes up on amd64 with UMA_MD_SMALL_ALLOC undefined, a
configuration required by some kernel sanitizers.
Discussed with: kib, rlibby
Reported by: andrew
Tested by: pho (i386 and amd64 with !UMA_MD_SMALL_ALLOC)
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D26851
uma_zone_reserve()), messages like the following appear on the console:
"Freed UMA keg (Test zone) was not empty (0 items). Lost 528 pages of
memory."
When keg_drain_domain() is draining the zone, it tries to keep the number
of items specified in the reservation. However, when we are destroying the
UMA zone, we do not need to keep those items. Therefore, when destroying a
non-secondary and non-cache zone, we should reset the keg reservation to 0
prior to draining the zone.
Reviewed by: markj
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D27129
This change adds support for transparent superpages for PowerPC64
systems using Hashed Page Tables (HPT). All pmap operations are
supported.
The changes were inspired by RISC-V implementation of superpages,
by @markj (r344106), but heavily adapted to fit PPC64 HPT architecture
and existing MMU OEA64 code.
While these changes are not better tested, superpages support is disabled by
default. To enable it, use vm.pmap.superpages_enabled=1.
In this initial implementation, when superpages are disabled, system
performance stays at the same level as without these changes. When
superpages are enabled, buildworld time increases a bit (~2%). However,
for workloads that put a heavy pressure on the TLB the performance boost
is much bigger (see HPC Challenge and pgbench on D25237).
Reviewed by: jhibbits
Sponsored by: Eldorado Research Institute (eldorado.org.br)
Differential Revision: https://reviews.freebsd.org/D25237
The 2 provided zones had inconsistent naming between each other
("int" and "64") and other allocator zones (which use bytes).
Follow malloc by naming them "pcpu-" + size in bytes.
This is a step towards replacing ad-hoc per-cpu zones with
general slabs.
This is mostly mechanical except for vmspace_exit(). There, use the new
refcount_release_if_last() to avoid switching to vmspace0 unless other
processes are sharing the vmspace. In that case, upon switching to
vmspace0 we can unconditionally release the reference.
Remove the volatile qualifier from vm_refcnt now that accesses are
protected using refcount(9) KPIs.
Reviewed by: alc, kib, mmel
MFC after: 1 month
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D27057
When a reserve of free items is configured for a zone, the reserve must
not be reclaimed under memory pressure. Modify keg_drain() to simply
respect the reserved pool.
While here remove an always-false uk_freef == NULL check (kegs that
shouldn't be drained should set _NOFREE instead), and make sure that the
keg_drain() KTR statement does not reference an uninitialized variable.
Reviewed by: alc, rlibby
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D26772
zone_import() fetches a free or partially free slab from the keg and
then uses its items to populate an array, typically filling a bucket.
If a single allocation causes the keg to drop below its minimum reserve,
the inner loop ends. However, if the bucket is still not full and
M_USE_RESERVE is specified, the outer loop will continue to fetch items
from the keg.
If M_USE_RESERVE is specified and the number of free items is below the
reserved limit, we should return only a single item. Otherwise, if the
bucket size is larger than the reserve, all of the reserved items may
end up in a single per-CPU bucket, invisible to other CPUs.
Reviewed by: rlibby
MFC after: 2 weeks
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D26771
Move dump_avail[] extern declaration and inlines into a new header
vm/vm_dumpset.h. This fixes default gcc build for mips.
Reviewed by: alc, scottph
Tested by: kevans (previous version)
Sponsored by: The FreeBSD Foundation
Differential revision: https://reviews.freebsd.org/D26741
The precedence of the '&' operator is less than of '+'. Added braces
do change the order of evaluation into the natural one, in my opinion.
On the other hand, the value of the expression should not change since
all elements should have page-aligned values.
This fixes a gcc warning reported.
Reported by: adrian
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
With helper page daemon threads, enabled by default in r364786, we
divide the inactive target by the number of threads, rounding down, and
sum the total number of pages freed by the threads. This sum is
compared with the original target, but by rounding down we might lose
pages, causing the page daemon control loop to conclude that inactive
queue scanning isn't keeping up with demand for free pages. Typically
this results in excessive swapping.
Fix the problem by accounting for the error in the main pagedaemon
thread's target. Note that by default the problem will manifest only in
systems with >16 CPUs in a NUMA domain.
Reviewed by: cem
Discussed with: dougm
Reported and tested by: dhw, glebius
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D26610
uma_zalloc_domain() allocates from the requested domain instead of
following a first-touch policy (the default for most zones). Currently
it is only used by malloc_domainset(), and consumers free returned items
with free(9) since r363834.
Previously uma_zalloc_domain() worked by always going to the keg for an
item. As a result, the use of UMA zone caches was unbalanced: we free
items to the caches, but always allocate from the keg, skipping the
caches.
Make some effort to allocate from the UMA caches when performing a
cross-domain allocation. This avoids blowing up the caches when
something is performing many transient allocations with
malloc_domainset().
Reported and tested by: dhw, glebius
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D26427
When SMR was introduced, zone_put_bucket() was changed to always place
full buckets at the end of the queue. However, it is generally
preferable to use recently used buckets since their items are more
likely to be resident in cache. So, for buckets that have no constraint
on item reuse, use a last-in-first-out ordering as we did before.
Reviewed by: rlibby
Tested by: dhw, glebius
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D26426
Currently we allocate and map zero-filled anonymous pages when dumping
core. This can result in lots of needless disk I/O and page
allocations. This change tries to make the core dumper more clever and
represent unbacked ranges of virtual memory by holes in the core dump
file.
Add a new page fault type, VM_FAULT_NOFILL, which causes vm_fault() to
clean up and return an error when it would otherwise map a zero-filled
page. Then, in the core dumper code, prefault all user pages and handle
errors by simply extending the size of the core file. This also fixes a
bug related to the fact that vn_io_fault1() does not attempt partial I/O
in the face of errors from vm_fault_quick_hold_pages(): if a truncated
file is mapped into a user process, an attempt to dump beyond the end of
the file results in an error, but this means that valid pages
immediately preceding the end of the file might not have been dumped
either.
The change reduces the core dump size of trivial programs by a factor of
ten simply by excluding unaccessed libc.so pages.
PR: 249067
Reviewed by: kib
Tested by: pho
MFC after: 1 month
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D26590
On an Ampere Altra system, the physical memory is populated
sparsely within the physical address space, with only about 0.4%
of physical addresses backed by RAM in the range [0, last_pa].
This is causing the vm_reserv_array to be over-sized by a few
orders of magnitude, wasting roughly 5 GiB on a system with
256 GiB of RAM.
The sparse allocation of vm_reserv_array is controlled by defining
VM_PHYSSEG_SPARSE, with the dense allocation still remaining for
platforms with VM_PHYSSEG_DENSE.
Reviewed by: markj, alc, kib
Approved by: scottl (implicit)
MFC after: 1 week
Sponsored by: Ampere Computing, Inc.
Differential Revision: https://reviews.freebsd.org/D26130
On Ampere Altra systems, the sparse population of RAM within the
physical address space causes the vm_page_dump bitmap to be much
larger than necessary, increasing the size from ~8 Mib to > 2 Gib
(and overflowing `int` for the size).
Changing the page dump bitmap also changes the minidump file
format, so changes are also necessary in libkvm.
Reviewed by: jhb
Approved by: scottl (implicit)
MFC after: 1 week
Sponsored by: Ampere Computing, Inc.
Differential Revision: https://reviews.freebsd.org/D26131
These definitions were repeated by all architectures, with small
variations. Consolidate the common definitons in machine
independent code and use bitset(9) macros for manipulation. Many
opportunities for deduplication remain in the machine dependent
minidump logic. The only intended functional change is increasing
the bit index type to vm_pindex_t, allowing the indexing of pages
with address of 8 TiB and greater.
Reviewed by: kib, markj
Approved by: scottl (implicit)
MFC after: 1 week
Sponsored by: Ampere Computing, Inc.
Differential Revision: https://reviews.freebsd.org/D26129
