This is a step towards being able to free pages without the page
lock held. The approach is simply to add an implementation of
vm_page_dequeue_deferred() which does not assert that the page
lock is held. Formally, the page lock is required to set
PGA_DEQUEUE, but in the case of vm_page_free_prep() we get the
same mutual exclusion for free by virtue of the fact that no
other references to the page may exist.
No functional change intended.
Reviewed by: kib (previous version)
MFC after: 2 weeks
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D19065
To detect the case where the page is already marked for a deferred
dequeue, we must read the "queue" and "aflags" fields in a
precise order. Otherwise, a race with a concurrent
vm_page_dequeue_complete() could leave the page with PGA_DEQUEUE
set despite it already having been dequeued. Fix the problem by
using vm_page_queue() to check the queue state, which correctly
handles the race.
Reviewed by: kib
Tested by: pho
MFC after: 3 days
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D19039
512GB of ZFS ABD ARC means abd_chunk zone of 128M 4KB items. To manage
them UMA tries to allocate 2GB hash table, which size does not fit into
the int variable, causing later allocation failure, which makes ARC shrink
back below the 512GB, not letting it to use more RAM. With this change I
easily reached >700GB ARC size on 768GB RAM machine.
MFC after: 1 week
Sponsored by: iXsystems, Inc.
Then bucket_alloc() also selects bucket size based on uz_count. However,
since zone lock is dropped, uz_count may reduce. In this case max may
be greater than ub_entries and that would yield into writing beyond end
of the allocation.
Reported by: pho
The iterator should be reinitialized after every successful slab
allocation. A request to advance the iterator is interpreted as
an allocation failure, so a sufficiently large preallocation would
cause the iterator to believe that all domains were exhausted,
resulting in a sleep with the keg lock held. [1]
Also, keg_alloc_slab() should pass the unmodified wait flag to the
item initialization routine, which may use it to perform allocations
from other zones.
Reported and tested by: slavah
Diagnosed by: kib [1]
Reviewed by: kib
MFC after: 1 week
Sponsored by: The FreeBSD Foundation
In order to allow single kernel to use PAE pagetables on i386 if
hardware supports it, and fall back to classic two-level paging
structures if not, superpage code should be able to adopt to either 2M
or 4M superpages size. There I make MI VM structures large enough to
track the biggest possible superpage, by allowing architecture to
define VM_NFREEORDER_MAX and VM_LEVEL_0_ORDER_MAX constants.
Corresponding VM_NFREEORDER and VM_LEVEL_0_ORDER symbols can be
defined as runtime values and must be less than the _MAX constants.
If architecture does not define _MAXs, it is assumed that _MAX ==
normal constant.
Reviewed by: markj
Tested by: pho (as part of the larger patch)
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D18853
Based on the description in Linux man page.
Reviewed by: markj, ngie (previous version)
Sponsored by: Mellanox Technologies
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D18837
This reduces amount of locking required for these zones.
Also, for cache only zones (UMA_ZFLAG_CACHE) accounting uz_items wasn't
correct at all, since they may allocate items directly from their backing
store and then free them via UMA underflowing uz_items.
Tested by: pho
atomic updates and reduces amount of data protected by zone lock.
During startup point these fields to EARLY_COUNTER. After startup
allocate them for all early zones.
Tested by: pho
o In vm_pager_bufferinit() create pbuf_zone and start accounting on how many
pbufs are we going to have set.
In various subsystems that are going to utilize pbufs create private zones
via call to pbuf_zsecond_create(). The latter calls uma_zsecond_create(),
and sets a limit on created zone. After startup preallocate pbufs according
to requirements of all pbuf zones.
Subsystems that used to have a private limit with old allocator now have
private pbuf zones: md(4), fusefs, NFS client, smbfs, VFS cluster, FFS,
swap, vnode pager.
The following subsystems use shared pbuf zone: cam(4), nvme(4), physio(9),
aio(4). They should have their private limits, but changing that is out of
scope of this commit.
o Fetch tunable value of kern.nswbuf from init_param2() and while here move
NSWBUF_MIN to opt_param.h and eliminate opt_swap.h, that was holding only
this option.
Default values aren't touched by this commit, but they probably should be
reviewed wrt to modern hardware.
This change removes a tight bottleneck from sendfile(2) operation, that
uses pbufs in vnode pager. Other pagers also would benefit from faster
allocation.
Together with: gallatin
Tested by: pho
two zones sharing a keg may have different limits. Now this is going
to work:
zone = uma_zcreate();
uma_zone_set_max(zone, limit);
zone2 = uma_zsecond_create(zone);
uma_zone_set_max(zone2, limit2);
Kegs no longer have uk_maxpages field, but zones have uz_items. When
set, it may be rounded up to minimum possible CPU bucket cache size.
For small limits bucket cache can also be reconfigured to be smaller.
Counter uz_items is updated whenever items transition from keg to a
bucket cache or directly to a consumer. If zone has uz_maxitems set and
it is reached, then we are going to sleep.
o Since new limits don't play well with multi-keg zones, remove them. The
idea of multi-keg zones was introduced exactly 10 years ago, and never
have had a practical usage. In discussion with Jeff we came to a wild
agreement that if we ever want to reintroduce the idea of a smart allocator
that would be able to choose between two (or more) totally different
backing stores, that choice should be made one level higher than UMA,
e.g. in malloc(9) or in mget(), or whatever and choice should be controlled
by the caller.
o Sleeping code is improved to account number of sleepers and wake them one
by one, to avoid thundering herd problem.
o Flag UMA_ZONE_NOBUCKETCACHE removed, instead uma_zone_set_maxcache()
KPI added. Having no bucket cache basically means setting maxcache to 0.
o Now with many fields added and many removed (no multi-keg zones!) make
sure that struct uma_zone is perfectly aligned.
Reviewed by: markj, jeff
Tested by: pho
Differential Revision: https://reviews.freebsd.org/D17773
from the local mapping.
Enable the setting by default.
The article behind the change: https://arxiv.org/abs/1901.01161
Reviewed by: markj
Discussed with: emaste
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D18764
Have ogetkerninfo, ogetpagesize, ogethostname, osethostname, and oaccept
declare o<foo>_args structs rather than non-compat ones. Due to a
failure to use NOARGS in most cases this adds only one new declaration.
No changes required in freebsd32 as only ogetpagesize() is implemented
and it has a 32-bit specific implementation.
Reviewed by: kib
Sponsored by: DARPA, AFRL
Differential Revision: https://reviews.freebsd.org/D15816
The type represents byte offset in the vm_object_t data space, which
does not span negative offsets in FreeBSD VM. The change matches byte
offset signess with the unsignedness of the vm_pindex_t which
represents the type of the page indexes in the objects.
This allows to remove the UOFF_TO_IDX() macro which was used when we
have to forcibly interpret the type as unsigned anyway. Also it fixes
a lot of implicit bugs in the device drivers d_mmap methods.
Reviewed by: alc, markj (previous version)
Tested by: pho
MFC after: 2 weeks
Sponsored by: The FreeBSD Foundation
If user configured the maxswapzone tunable, just take the literal
value for the initial zone sizing attempt. Before, it was only
possible to reduce the zone by the tunable.
While there, correct the message which was not correct when zone
creation rounded the size up.
Reported by: jmg
Reviewed by: markj
MFC after: 1 week
Sponsored by: The FreeBSD Foundation
Differential revision: https://reviews.freebsd.org/D18381
This applies the fix in r283924 to the vm.objects sysctl
added by r283624 so the output will include the vnode
information (i.e. path) for tmpfs objects.
Reviewed by: kib, dab
MFC after: 2 weeks
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D2724
Otherwise the free page count will not accurately reflect the physical
page allocator's state. On 11 this can trigger panics in
vm_page_alloc() since the allocator state and free page count are
updated atomically and we expect them to stay in sync. On 12 the
bug would manifest as threads looping in vm_page_alloc().
PR: 231296
Reported by: mav, wollman, Rainer Duffner, Josh Gitlin
Reviewed by: alc, kib, mav
MFC after: 3 days
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D18374
several pages, but leaves no space for struct uma_slab at the end we
miscalculate number of pages by one. Totally mimic keg_large_init() math
here to cover that problem.
Reported by: gallatin
is calculated to guarantee that struct uma_slab is placed at pointer size
alignment. Calculation of real struct uma_slab size is done in keg_ctor()
and yet again in keg_large_init(), to check if we need an extra page. This
calculation can actually be performed at compile time.
- Add SIZEOF_UMA_SLAB macro to calculate size of struct uma_slab placed at
an end of a page with alignment requirement.
- Use SIZEOF_UMA_SLAB in keg_ctor() and in keg_large_init(). This is a not
a functional change.
- Use SIZEOF_UMA_SLAB in UMA_SLAB_SPACE definition and in keg_small_init().
This is a potential bugfix, but in reality I don't think there are any
systems affected, since compiler aligns struct uma_slab anyway.
All vmspace_alloc() callers know which kind of pmap they allocate.
Reviewed by: alc, markj (previous version)
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D18329
According to markj@:
pageproc contains the page daemon and laundry threads, which are
responsible for managing the LRU page queues and writing back dirty
pages. vmproc's main task is to swap out kernel stacks when the system
is under memory pressure, and swap them back in when necessary. It's a
somewhat legacy component of the system and isn't required. You can
build a kernel without it by specifying "options NO_SWAPPING" (which is
a somewhat misleading name), in which vm_swapout_dummy.c is compiled
instead of vm_swapout.c.
Based on this, we want pageproc to emulate kswapd, not vmproc.
Reviewed by: markj
Differential Revision: https://reviews.freebsd.org/D18061
These are used by kms-drm to determine various heuristics relate
memory conditions.
The number of free swap pages is just a variable, and it can be
much cheaper by either adding a new getter, or simply extern'ing
swap_total. However, this patch opts to use the more expensive,
existing interface - since this isn't an operation in a high per
path.
This allows us to remove some more gpl linuxkpi and do the follo
kms-drm:
git rm linuxkpi/gplv2/include/linux/swap.h
Reviewed by: mmacy, Johannes Lundberg <johalun0@gmail.com>
Approved by: emaste (mentor)
Differential Revision: https://reviews.freebsd.org/D18052
functions. Notably, reflow the text of some comments so that they
occupy fewer lines, and introduce an assertion in one of the new
helper functions so that it is not misused by a future caller.
In collaboration with: Doug Moore <dougm@rice.edu>
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D17635
In particular, track the current size of the cache and maintain an
estimate of its working set size. This will be used to decide how
much to shrink various caches when the kernel attempts to reclaim
pages. As a secondary effect, it makes statistics aggregation (done
by, e.g., vmstat -z) cheaper since sysctl_vm_zone_stats() no longer
needs to iterate over lists of cached buckets.
Discussed with: alc, glebius, jeff
Tested by: pho (previous version)
MFC after: 1 month
Differential Revision: https://reviews.freebsd.org/D16666
r336984 exposed the bug fixed in r340241, leading to the initial revert
while the bug was being hunted down. Now that the bug is fixed, we
can revert the revert.
Discussed with: alc
MFC after: 3 days
This was introduced in r326329 and explains the crashes mentioned in
the commit log message for r339934. In particular, on INVARIANTS
kernels, UMA trashing causes the loop to exit early, leaving swap
blocks behind when they should have been freed. After r336984 this
became more problematic since new anonymous mappings were more
likely to reuse swapped-out subranges of existing VM objects, so faults
would trigger pageins of freed memory rather than returning zeroed
pages.
Reviewed by: kib
MFC after: 3 days
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D17897
These submaps are used for mapping pipe buffers and execv() argument
strings respectively, so there's no need for such mappings to have
execute permissions.
Reported by: jhb
Reviewed by: alc, jhb, kib
MFC after: 2 weeks
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D17827
In practice it is always initialized because nfreed must be positive
in order to trigger background laundering, but this isn't obvious.
CID: 1387997
MFC after: 1 week
Initializing the eflags field of the map->header entry to a value with a
unique new bit set makes a few comparisons to &map->header unnecessary.
Submitted by: Doug Moore <dougm@rice.edu>
Reviewed by: alc, kib
Tested by: pho
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D14005
It appears to be responsible for random segfaults observed when lots
of paging activity is taking place, but the root cause is not yet
understood.
Requested by: alc
MFC after: now
Remove malloc_domain(9) and most other _domain KPIs added in r327900.
The new functions allow the caller to specify a general NUMA domain
selection policy, rather than specifically requesting an allocation from
a specific domain. The latter policy tends to interact poorly with
M_WAITOK, resulting in situations where a caller is blocked indefinitely
because the specified domain is depleted. Most existing consumers of
the _domain KPIs are converted to instead use a DOMAINSET_PREF() policy,
in which we fall back to other domains to satisfy the allocation
request.
This change also defines a set of DOMAINSET_FIXED() policies, which
only permit allocations from the specified domain.
Discussed with: gallatin, jeff
Reported and tested by: pho (previous version)
MFC after: 2 weeks
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D17418
- In uma_prealloc(), we need to check for an empty domain before the
first allocation attempt, not after. Fix this by switching
uma_prealloc() to use a vm_domainset iterator, which addresses the
secondary issue of using a signed domain identifier in round-robin
iteration.
- Don't automatically create a page daemon for domain 0.
- In domainset_empty_vm(), recompute ds_cnt and ds_order after
excluding empty domains; otherwise we may frequently specify an empty
domain when calling in to the page allocator, wasting CPU time.
Convert DOMAINSET_PREF() policies for empty domains to round-robin.
- When freeing bootstrap pages, don't count them towards the per-domain
total page counts for now: some vm_phys segments are created before
the SRAT is parsed and are thus always identified as being in domain 0
even when they are not. Then, when bootstrap pages are freed, they
are added to a domain that we had previously thought was empty. Until
this is corrected, we simply exclude them from the per-domain page
count.
Reported and tested by: Rajesh Kumar <rajfbsd@gmail.com>
Reviewed by: gallatin
MFC after: 2 weeks
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D17704
on-write faults. On a page fault, when we call vm_fault_prefault(), it
probes the pmap and the shadow chain of vm objects to see if there are
opportunities to create read and/or execute-only mappings to neighoring
pages. For example, in the case of hard faults, such effort typically pays
off, that is, mappings are created that eliminate future soft page faults.
However, in the the case of soft, copy-on-write faults, the effort very
rarely pays off. (See the review for some specific data.)
Reviewed by: kib, markj
MFC after: 3 weeks
Differential Revision: https://reviews.freebsd.org/D17367
Previously, it used a hand-rolled round-robin iterator. This meant that
the minskip logic in r338507 didn't apply to UMA allocations, and also
meant that we would call vm_wait() for individual domains rather than
permitting an allocation from any domain with sufficient free pages.
Discussed with: jeff
Tested by: pho
MFC after: 1 week
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D17420
Before this change we had two flavours of vm_domainset iterators: "page"
and "malloc". The latter was only used for kmem_*() and hard-coded its
behaviour based on kernel_object's policy. Moreover, its use contained
a race similar to that fixed by r338755 since the kernel_object's
iterator was being run without the object lock.
In some cases it is useful to be able to explicitly specify a policy
(domainset) or policy+iterator (domainset_ref) when performing memory
allocations. To that end, refactor the vm_dominset_* KPI to permit
this, and get rid of the "malloc" domainset_iter KPI in the process.
Reviewed by: jeff (previous version)
Tested by: pho (part of a larger patch)
MFC after: 2 weeks
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D17417
