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
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
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
cache, then we put new bucket on generic bucket cache. However, code didn't
honor UMA_ZONE_NOBUCKETCACHE flag, so potentially we could start a cache
on a zone that clearly forbids that. Fix this.
Reviewed by: markj
The AMD Threadripper 2990WX is basically a slightly crippled Epyc.
Rather than having 4 memory controllers, one per NUMA domain, it has
only 2 memory controllers enabled. This means that only 2 of the
4 NUMA domains can be populated with physical memory, and the
others are empty.
Add support to FreeBSD for empty NUMA domains by:
- creating empty memory domains when parsing the SRAT table,
rather than failing to parse the table
- not running the pageout deamon threads in empty domains
- adding defensive code to UMA to avoid allocating from empty domains
- adding defensive code to cpuset to avoid binding to an empty domain
Thanks to Jeff for suggesting this strategy.
Reviewed by: alc, markj
Approved by: re (gjb@)
Differential Revision: https://reviews.freebsd.org/D1683
We drop the keg lock when we go to actually allocate the slab, allowing
other threads to advance the cursor. This can cause us to exit the
round-robin loop before having attempted allocations from all domains,
resulting in a hang during a subsequent blocking allocation attempt from
a depleted domain.
Reported and tested by: Jan Bramkamp <crest@bultmann.eu>
Reviewed by: alc, cem
Approved by: re (gjb)
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D17209
given in random(4).
This includes updating of the relevant man pages, and no-longer-used
harvesting parameters.
Ensure that the pseudo-unit-test still does something useful, now also
with the "other" algorithm instead of Yarrow.
PR: 230870
Reviewed by: cem
Approved by: so(delphij,gtetlow)
Approved by: re(marius)
Differential Revision: https://reviews.freebsd.org/D16898
error in the function hypercall_memfree(), where the wrong arena was being
passed to kmem_free().
Introduce a per-page flag, VPO_KMEM_EXEC, to mark physical pages that are
mapped in kmem with execute permissions. Use this flag to determine which
arena the kmem virtual addresses are returned to.
Eliminate UMA_SLAB_KRWX. The introduction of VPO_KMEM_EXEC makes it
redundant.
Update the nearby comment for UMA_SLAB_KERNEL.
Reviewed by: kib, markj
Discussed with: jeff
Approved by: re (marius)
Differential Revision: https://reviews.freebsd.org/D16845
became unused in FreeBSD 12.x as a side-effect of the NUMA-related
changes.)
Reviewed by: kib, markj
Discussed with: jeff, re@
Differential Revision: https://reviews.freebsd.org/D16825
The domain and flags parameters suffice. In fact, the related functions
kmem_alloc_{attr,contig}_domain() don't have an arena parameter.
Reviewed by: kib, markj
Differential Revision: https://reviews.freebsd.org/D16713
r336020 introduced pcpu_page_alloc(), replacing page_alloc() as the
backend allocator for PCPU UMA zones. Unlike page_alloc(), it does
not honour malloc(9) flags such as M_ZERO or M_NODUMP, so fix that.
r336020 also changed counter(9) to initialize each counter using a
CPU_FOREACH() loop instead of an SMP rendezvous. Before SI_SUB_CPU,
smp_rendezvous() will only execute the callback on the current CPU
(i.e., CPU 0), so only one counter gets zeroed. The rest are zeroed
by virtue of the fact that UMA gratuitously zeroes slabs when importing
them into a zone.
Prior to SI_SUB_CPU, all_cpus is clear, so with r336020 we weren't
zeroing vm_cnt counters during boot: the CPU_FOREACH() loop had no
effect, and pcpu_page_alloc() didn't honour M_ZERO. Fix this by
iterating over the full range of CPU IDs when zeroing counters,
ignoring whether the corresponding bits in all_cpus are set.
Reported and tested by: pho (previous version)
Reviewed by: kib (previous version)
Differential Revision: https://reviews.freebsd.org/D16190
- Change pcpu zone consumers to use a stride size of PAGE_SIZE.
(defined as UMA_PCPU_ALLOC_SIZE to make future identification easier)
- Allocate page from the correct domain for a given cpu.
- Don't initialize pc_domain to non-zero value if NUMA is not defined
There are some misconceptions surrounding this field. It is the
_VM_ NUMA domain and should only ever correspond to valid domain
values as understood by the VM.
The former slab size of sizeof(struct pcpu) was somewhat arbitrary.
The new value is PAGE_SIZE because that's the smallest granularity
which the VM can allocate a slab for a given domain. If you have
fewer than PAGE_SIZE/8 counters on your system there will be some
memory wasted, but this is obviously something where you want the
cache line to be coming from the correct domain.
Reviewed by: jeff
Sponsored by: Limelight Networks
Differential Revision: https://reviews.freebsd.org/D15933
Most kernel memory that is allocated after boot does not need to be
executable. There are a few exceptions. For example, kernel modules
do need executable memory, but they don't use UMA or malloc(9). The
BPF JIT compiler also needs executable memory and did use malloc(9)
until r317072.
(Note that a side effect of r316767 was that the "small allocation"
path in UMA on amd64 already returned non-executable memory. This
meant that some calls to malloc(9) or the UMA zone(9) allocator could
return executable memory, while others could return non-executable
memory. This change makes the behavior consistent.)
This change makes malloc(9) return non-executable memory unless the new
M_EXEC flag is specified. After this change, the UMA zone(9) allocator
will always return non-executable memory, and a KASSERT will catch
attempts to use the M_EXEC flag to allocate executable memory using
uma_zalloc() or its variants.
Allocations that do need executable memory have various choices. They
may use the M_EXEC flag to malloc(9), or they may use a different VM
interfact to obtain executable pages.
Now that malloc(9) again allows executable allocations, this change also
reverts most of r317072.
PR: 228927
Reviewed by: alc, kib, markj, jhb (previous version)
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D15691
Per-cpu zone allocations are very rarely done compared to regular zones.
The intent is to avoid pessimizing the latter case with per-cpu specific
code.
In particular contrary to the claim in r334824, M_ZERO is sometimes being
used for such zones. But the zeroing method is completely different and
braching on it in the fast path for regular zones is a waste of time.
Turns out there is code which ends up passing M_ZERO to counters.
Since counters zero unconditionally on their own, just ignore drop the
flag in that place.
Nothing in the tree uses it and pcpu zones have a fundamentally different use
case than the regular zones - they are not supposed to be allocated and freed
all the time.
This reduces pollution in the allocation fast path.
trashing freed memory and checking that allocated memory is properly
trashed, and also of keeping a bitset of freed items. Trashing/checking
creates a lot of CPU cache poisoning, while keeping debugging bitsets
consistent creates a lot of contention on UMA zone lock(s). The performance
difference between INVARIANTS kernel and normal one is mostly attributed
to UMA debugging, rather than to all KASSERT checks in the kernel.
Add loader tunable vm.debug.divisor that allows either to turn off UMA
debugging completely, or turn it on only for a fraction of allocations,
while still running all KASSERTs in kernel. That allows to run INVARIANTS
kernels in production environments without reducing load by orders of
magnitude, but still doing useful extra checks.
Default value is 1, meaning debug every allocation. Value of 0 would
disable UMA debugging completely. Values above 1 enable debugging only
for every N-th item. It isn't possible to strictly follow the number,
but still amount of debugging is reduced roughly by (N-1)/N percent.
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D15199
Cached counters are typically zero at this point so it performs
avoidable atomics. Everything reading them also reads the cached
ones, thus there is really no point.
Reviewed by: jeff
This allows the creation of zones which don't do any caching in front of
the keg. If the zone is a cache zone, this means that UMA will not
attempt any memory allocations when allocating an item from the backend.
This is intended for use after a panic by netdump, but likely has other
applications.
Reviewed by: kib
MFC after: 2 weeks
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D15184
single slab, but with alignment adjustment it won't. Again, when
there is only one item in a slab alignment can be ignored. See
previous revision of this file for more info.
PR: 227116
and zone has a large alignment. With alignment taken into
account uk_rsize will be greater than space in a slab. However,
since we have only one item per slab, it is always naturally
aligned.
Code that will panic before this change with 4k page:
z = uma_zcreate("test", 3984, NULL, NULL, NULL, NULL, 31, 0);
uma_zalloc(z, M_WAITOK);
A practical scenario to hit the panic is a machine with 56 CPUs
and 2 NUMA domains, which yields in zone size of 3984.
PR: 227116
MFC after: 2 weeks
a cache of fully populated buckets. This will be used in a follow-on
commit.
The flag idea was originally from markj.
Reviewed by: markj, kib
Tested by: pho
Sponsored by: Netflix, Dell/EMC Isilon
copyout(9) while owning zone lock.
Despite old value sysctl buffer is wired, spurious faults might still
occur.
Note that we still own the uma_rwlock there, but this lock does not
participate in sensitive lock orders.
Reported and tested by: pho (as part of the larger patch)
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
size of UMA zone allocation is greater than page size. In this case zone
of zones can not use UMA_MD_SMALL_ALLOC, and we need to postpone switch
off of this zone from startup_alloc() until full launch of VM.
o Always supply number of VM zones to uma_startup_count(). On machines
with UMA_MD_SMALL_ALLOC ignore it completely, unless zsize goes over
a page. In the latter case account VM zones for number of allocations
from the zone of zones.
o Rewrite startup_alloc() so that it will immediately switch off from
itself any zone that is already capable of running real alloc.
In worst case scenario we may leak a single page here. See comment
in uma_startup_count().
o Hardcode call to uma_startup2() into vm_mem_init(). Otherwise some
extra SYSINITs, e.g. vm_page_init() may sneak in before.
o While here, remove uma_boot_pages_mtx. With recent changes to boot
pages calculation, we are guaranteed to use all of the boot_pages
in the early single threaded stage.
Reported & tested by: mav
o Most of startup zones have struct uma_slab embedded into the slab,
so provide macro UMA_SLAB_SPACE and use it instead of UMA_SLAB_SIZE,
when calculating how many pages would certain kind of allocations
require. Some zones are offpage, so we might have a positive inaccuracy.
o The keg for the zone of zones is allocated "dynamically", so we
need +1 when calculating amount of pages for kegs. [1]
o The zones of zones and zones of kegs have arbitrary alignment of 32,
and this also needs to be accounted for. [2]
While here, spread more comments and improve diagnostic messages.
Reported by: pho [1], jtl [2]
global to per-domain state. Protect reservations with the free lock
from the domain that they belong to. Refactor to make vm domains more
of a first class object.
Reviewed by: markj, kib, gallatin
Tested by: pho
Sponsored by: Netflix, Dell/EMC Isilon
Differential Revision: https://reviews.freebsd.org/D14000
for UMA startup.
o Introduce another stage of UMA startup, which is entered after
vm_page_startup() finishes. After this stage we don't yet enable buckets,
but we can ask VM for pages. Rename stages to meaningful names while here.
New list of stages: BOOT_COLD, BOOT_STRAPPED, BOOT_PAGEALLOC, BOOT_BUCKETS,
BOOT_RUNNING.
Enabling page alloc earlier allows us to dramatically reduce number of
boot pages required. What is more important number of zones becomes
consistent across different machines, as no MD allocations are done before
the BOOT_PAGEALLOC stage. Now only UMA internal zones actually need to use
startup_alloc(), however that may change, so vm_page_startup() provides
its need for early zones as argument.
o Introduce uma_startup_count() function, to avoid code duplication. The
functions calculates sizes of zones zone and kegs zone, and calculates how
many pages UMA will need to bootstrap.
It counts not only of zone structures, but also of kegs, slabs and hashes.
o Hide uma_startup_foo() declarations from public file.
o Provide several DIAGNOSTIC printfs on boot_pages usage.
o Bugfix: when calculating zone of zones size use (mp_maxid + 1) instead of
mp_ncpus. Use resulting number not only in the size argument to zone_ctor()
but also as args.size.
Reviewed by: imp, gallatin (earlier version)
Differential Revision: https://reviews.freebsd.org/D14054
domains can be done by the _domain() API variants. UMA also supports a
first-touch policy via the NUMA zone flag.
The slab layer is now segregated by VM domains and is precise. It handles
iteration for round-robin directly. The per-cpu cache layer remains
a mix of domains according to where memory is allocated and freed. Well
behaved clients can achieve perfect locality with no performance penalty.
The direct domain allocation functions have to visit the slab layer and
so require per-zone locks which come at some expense.
Reviewed by: Attilio (a slightly older version)
Tested by: pho
Sponsored by: Netflix, Dell/EMC Isilon
rather than kmem arena size to determine available memory.
Initialize the UMA limit to LONG_MAX to avoid spurious wakeups on boot before
the real limit is set.
PR: 224330 (partial), 224080
Reviewed by: markj, avg
Sponsored by: Netflix / Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D13494
atomic_set_*() sets a bit in the target memory location, so
atomic_set_int(&uma_reclaim_needed, 0) does not do what it looks like
it does.
PR: 224080
Reviewed by: jeff, kib
Differential Revision: https://reviews.freebsd.org/D13412
The arena argument to kmem_*() is now only used in an assert. A follow-up
commit will remove the argument altogether before we freeze the API for the
next release.
This replaces the hard limit on kmem size with a soft limit imposed by UMA. When
the soft limit is exceeded we periodically wakeup the UMA reclaim thread to
attempt to shrink KVA. On 32bit architectures this should behave much more
gracefully as we exhaust KVA. On 64bit the limits are likely never hit.
Reviewed by: markj, kib (some objections)
Discussed with: alc
Tested by: pho
Sponsored by: Netflix / Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D13187
Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.
The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.
No functional change intended.
similar to the kernel memory allocator.
This simplifies NUMA allocation because the domain will be known at wait
time and races between failure and sleeping are eliminated. This also
reduces boilerplate code and simplifies callers.
A wait primitive is supplied for uma zones for similar reasons. This
eliminates some non-specific VM_WAIT calls in favor of more explicit
sleeps that may be satisfied without new pages.
Reviewed by: alc, kib, markj
Tested by: pho
Sponsored by: Netflix, Dell/EMC Isilon
Kegs for internal zones always keep the slab header in the slab itself.
Therefore, when determining the allocation size, we need to take the
slab header size into account.
Reported and tested by: ae, rakuco
Reviewed by: avg
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D12342
While these locks are guarnteed to not share their respective cache lines,
their current placement leaves unnecessary holes in lines which preceeded them.
For instance the annotation of vm_page_queue_free_mtx allows 2 neighbour
cachelines (previously separate by the lock) to be collapsed into 1.
The annotation is only effective on architectures which have it implemented in
their linker script (currently only amd64). Thus locks are not converted to
their not-padaligned variants as to not affect the rest.
MFC after: 1 week
internal zones only. This allows to create new zones at early stages
of boot, without need to mark them as internal to UMA, which isn't
always true.
Reviewed by: alc
It is simply a contigous virtual memory pointer and number of pages.
There is no need to build a linked list here. Just increment pointer
and decrement counter. The only functional difference to old allocator
is that before we gave pages from topmost and down to lowest, and now
we give them in normal ascending order.
While here remove padalign from a mutex that is unused at runtime.
Reviewed by: alc
