In many cases the page is not enqueued so the change will have no
effect. However, the change is needed to support an optimization in
the fault handler and in some cases (sendfile, the buffer cache) it
was being emulated by the caller anyway.
Reviewed by: alc
Tested by: pho
MFC after: 2 weeks
X-Differential Revision: https://reviews.freebsd.org/D14625
The new page does not belong to a VM object, but the page daemon does
not expect to encounter such pages.
Reviewed by: alc, kib
Tested by: pho
MFC after: 1 week
X-Differential Revision: https://reviews.freebsd.org/D14625
vmd_free_count manipulation. Reduce the scope of the free lock by
using a pageout lock to synchronize sleep and wakeup. Only trigger
the pageout daemon on transitions between states. Drive all wakeup
operations directly as side-effects from freeing memory rather than
requiring an additional function call.
Reviewed by: markj, kib
Tested by: pho
Sponsored by: Netflix, Dell/EMC Isilon
Differential Revision: https://reviews.freebsd.org/D14612
There, the pages freed might be managed but the page's lock is not
owned. For KPI correctness, the page lock is requried around the call
to vm_page_free_prep(), which is asserted. Reclaim loop already did
the work which could be done by vm_page_free_prep(), so the lock is
not needed and the only consequence of not owning it is the assert
trigger.
Instead of adding the locking to satisfy the assert, revert to the
code that calls vm_page_free_phys() directly.
Reported by: pho
Discussed with: jeff
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
After r328977, a wired page m may have m->queue != PQ_NONE.
Reviewed by: kib
X-MFC with: r328977
Differential Revision: https://reviews.freebsd.org/D14485
use it to regulate page daemon output.
This provides much smoother and more responsive page daemon output, anticipating
demand and avoiding pageout stalls by increasing the number of pages to match
the workload. This is a reimplementation of work done by myself and mlaier at
Isilon.
Reviewed by: bsdimp
Tested by: pho
Sponsored by: Netflix, Dell/EMC Isilon
Differential Revision: https://reviews.freebsd.org/D14402
Make vm_wait() take the vm_object argument which specifies the domain
set to wait for the min condition pass. If there is no object
associated with the wait, use curthread' policy domainset. The
mechanics of the wait in vm_wait() and vm_wait_domain() is supplied by
the new helper vm_wait_doms(), which directly takes the bitmask of the
domains to wait for passing min condition.
Eliminate pagedaemon_wait(). vm_domain_clear() handles the same
operations.
Eliminate VM_WAIT and VM_WAITPFAULT macros, the direct functions calls
are enough.
Eliminate several control state variables from vm_domain, unneeded
after the vm_wait() conversion.
Scetched and reviewed by: jeff
Tested by: pho
Sponsored by: The FreeBSD Foundation, Mellanox Technologies
Differential revision: https://reviews.freebsd.org/D14384
significant source of cache line contention from vm_page_alloc(). Use
accessors and vm_page_unwire_noq() so that the mechanism can be easily
changed in the future.
Reviewed by: markj
Discussed with: kib, glebius
Tested by: pho (earlier version)
Sponsored by: Netflix, Dell/EMC Isilon
Differential Revision: https://reviews.freebsd.org/D14273
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]
Previously, wiring a page would cause it to be removed from its page
queue. In the common case, unwiring causes it to be enqueued at the tail
of that page queue. This change modifies vm_page_wire() to not dequeue
the page, thus avoiding the highly contended page queue locks. Instead,
vm_page_unwire() takes care of requeuing the page as a single operation,
and the page daemon dequeues wired pages as they are encountered during
a queue scan to avoid needlessly revisiting them later. For pages in
PQ_ACTIVE we do even better, since a requeue is unnecessary.
The change improves scalability for some common workloads. For instance,
threads wiring pages into the buffer cache no longer need to modify
global page queues, and unwiring is usually done by the bufspace thread,
so concurrency is not as much of an issue. As another example, many
sysctl handlers wire the output buffer to avoid faults on copyout, and
since the buffer is likely to be in PQ_ACTIVE, we now entirely avoid
modifying the page queue in this case.
The change also adds a block comment describing some properties of
struct vm_page's reference counters, and the busy lock.
Reviewed by: jeff
Discussed with: alc, kib
MFC after: 1 month
Differential Revision: https://reviews.freebsd.org/D11943
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
o Call uma_startup1() after initializing kmem, vmem and domains.
o Include 8 eight VM startup pages into uma_startup_count() calculation.
o Account for vmem_startup() and vm_map_startup() preallocating pages.
o Account for extra two allocations done by kmem_init() and vmem_create().
o Hardcode the place of execution of vm_radix_reserve_kva(). Using SYSINIT
allowed several other SYSINITs to sneak in before it, thus bumping
requirement for amount of boot pages.
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
kernel by PHYS_TO_DMAP() as previously present on amd64, arm64, riscv, and
powerpc64. This introduces a new MI macro (PMAP_HAS_DMAP) that can be
evaluated at runtime to determine if the architecture has a direct map;
if it does not (or does) unconditionally and PMAP_HAS_DMAP is either 0 or
1, the compiler can remove the conditional logic.
As part of this, implement PHYS_TO_DMAP() on sparc64 and mips64, which had
similar things but spelled differently. 32-bit MIPS has a partial direct-map
that maps poorly to this concept and is unchanged.
Reviewed by: kib
Suggestions from: marius, alc, kib
Runtime tested on: amd64, powerpc64, powerpc, mips64
userspace to control NUMA policy administratively and programmatically.
Implement domainset based iterators in the page layer.
Remove the now legacy numa_* syscalls.
Cleanup some header polution created by having seq.h in proc.h.
Reviewed by: markj, kib
Discussed with: alc
Tested by: pho
Sponsored by: Netflix, Dell/EMC Isilon
Differential Revision: https://reviews.freebsd.org/D13403
Both issues caused the page daemon to erroneously go to sleep when
applications are consuming free pages at a high rate, leaving the
application threads blocked in VM_WAIT.
1) After completing an inactive queue scan, concurrent allocations may
have prevented the page daemon from meeting the v_free_min threshold.
In this case, the page daemon was going to sleep even when the
inactive queue contained plenty of clean pages.
2) pagedaemon_wakeup() may be called without the free queues lock held.
This can lead to a lost wakeup if a call occurs after the page daemon
clears vm_pageout_wanted but before going to sleep.
Fix 1) by ensuring that we start a new inactive queue scan immediately
if v_free_count < v_free_min after a prior scan.
Fix 2) by adding a new subroutine, pagedaemon_wait(), called from
vm_wait() and vm_waitpfault(). It wakes up the page daemon if either
vm_pages_needed or vm_pageout_wanted is false, and atomically sleeps
on v_free_count.
Reported by: jeff
Reviewed by: alc
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D13424
Commit r326346 moved domain iterators from physical layer to vm_page one,
but it also removed translation of freelist to flind for
vm_page_alloc_freelist() call. Before it expects VM_FREELIST_ parameter,
but after it expect freelist index.
On small WiFi boxes with few megabytes of RAM, there is only one freelist
VM_FREELIST_LOWMEM (1) and there is no VM_FREELIST_DEFAULT(0) (see file
sys/mips/include/vmparam.h). It results in freelist 1 with flind 0.
At first, this commit renames flind to freelist in vm_page_alloc_freelist
to avoid misunderstanding about input parameters. Then on physical layer it
restores translation for correct handling of freelist parameter.
Reported by: landonf
Reviewed by: jeff
Differential Revision: https://reviews.freebsd.org/D13351
This gives a marginal improvement in the vm_page_array initialization
time. Also garbage-collect the now-unused vm_phys_paddr_to_segind().
Reviewed by: alc, kib
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D13270
Some drm2 drivers will set PG_FICTITIOUS in physical pages in order to
satisfy the OBJT_MGTDEVICE object interface, so a scan may encounter
fictitous pages. For now, allow for this possibility; such pages will be
skipped later in the scan since they are wired.
Reported by: avg
Reviewed by: kib
MFC after: 1 week
Mainly focus on files that use BSD 3-Clause license.
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.
Special thanks to Wind River for providing access to "The Duke of
Highlander" tool: an older (2014) run over FreeBSD tree was useful as a
starting point.
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
A fictitious page is always wired, so there is no point in trying to
remove one from the page queues.
Completely remove one inaccurate comment from vm_page_free_prep() and
correct another.
Reviewed by: kib, markj
MFC after: 1 week
This catches some rare mysterious failures at the source. The check
is only performed on architectures which implement direct map, and
only enabled with option DIAGNOSTIC, similar to other costly
consistency checks.
Reviewed by: alc, markj
Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks
The variable is modified with the highly contended page free queue lock.
It unnecessarily shares a cacheline with purely read-only fields and is
re-read after the lock is dropped in the page allocation code making the
hold time longer.
Pad the variable just like the others and store the value as found with
the lock held instead of re-reading.
Provides a modest 1%-ish speed up in concurrent page faults.
Reviewed by: kib, markj
Differential Revision: https://reviews.freebsd.org/D12665
vm_page_try_to_free() is testing conditions, like clean versus dirty,
that only vary in managed pages.
Suggested by: kib
Reviewed by: markj
X-MFC after: never
can be avoided when the page's containing object has a reference count of
zero. (If the object has a reference count of zero, then none of its pages
can possibly be mapped.)
Address nearby style issues in vm_page_try_to_free(), and change its
return type to "bool".
Reviewed by: kib, markj
MFC after: 1 week
and insertion into the phys allocator free queues vm_page_free_phys().
Also provide a wrapper vm_page_free_phys_pglist() for batched free.
Reviewed by: alc, markj
Tested by: mjg (previous version)
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
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
lock if both old and new pages use the same underlying lock. Convert
existing places to use the helper instead of inlining it. Use the
optimization in vm_object_page_remove().
Suggested and reviewed by: alc, markj
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
We currently initialize the vm_page array in three passes: one to zero
the array, one to initialize the "order" field of each page (necessary
when inserting them into the vm_phys buddy allocator one-by-one), and
one to initialize the remaining non-zero fields and individually insert
each page into the allocator.
Merge the three passes into one following a suggestion from alc:
initialize vm_page fields in a single pass, and use vm_phys_free_contig()
to efficiently insert physical memory segments into the buddy allocator.
This reduces the initialization time to a third or a quarter of what it
was before on most systems that I tested.
Reviewed by: alc, kib
MFC after: 3 weeks
Differential Revision: https://reviews.freebsd.org/D12248
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
This is a variant of vm_page_alloc() which accepts an additional parameter:
the page in the object with largest index that is smaller than the requested
index. vm_page_alloc() finds this page using a lookup in the object's radix
tree, but in some cases its identity is already known, allowing the lookup
to be elided.
Modify kmem_back() and vm_page_grab_pages() to use vm_page_alloc_after().
vm_page_alloc() is converted into a trivial wrapper of
vm_page_alloc_after().
Suggested by: alc
Reviewed by: alc, kib
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D11984
vm_page_grab() on consecutive page indices. Besides simplifying the code
in the caller, vm_page_grab_pages() allows for batching optimizations.
For example, the current implementation replaces calls to vm_page_lookup()
on consecutive page indices by cheaper calls to vm_page_next().
Reviewed by: kib, markj
Tested by: pho (an earlier version)
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D11926
superpage all belong to the same object. To date, that check has not been
needed, but upcoming changes require it. (See the Differential Revision.)
Reviewed by: kib, markj
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D11556
r31386 changed how the size of the VM page array was calculated to be
less wasteful. For most systems, the amount of memory is divided by
the overhead required by each page (a page of data plus a struct vm_page)
to determine the maximum number of available pages. However, if the
remainder for the first non-available page was at least a page of data
(so that the only memory missing was a struct vm_page), this last page
was left in phys_avail[] but was not allocated an entry in the VM page
array. Handle this case by explicitly excluding the page from
phys_avail[].
Reviewed by: alc
Sponsored by: DARPA / AFRL
Differential Revision: https://reviews.freebsd.org/D11000
in place. To do per-cpu stats, convert all fields that previously were
maintained in the vmmeters that sit in pcpus to counter(9).
- Since some vmmeter stats may be touched at very early stages of boot,
before we have set up UMA and we can do counter_u64_alloc(), provide an
early counter mechanism:
o Leave one spare uint64_t in struct pcpu, named pc_early_dummy_counter.
o Point counter(9) fields of vmmeter to pcpu[0].pc_early_dummy_counter,
so that at early stages of boot, before counters are allocated we already
point to a counter that can be safely written to.
o For sparc64 that required a whole dummy pcpu[MAXCPU] array.
Further related changes:
- Don't include vmmeter.h into pcpu.h.
- vm.stats.vm.v_swappgsout and vm.stats.vm.v_swappgsin changed to 64-bit,
to match kernel representation.
- struct vmmeter hidden under _KERNEL, and only vmstat(1) is an exclusion.
This is based on benno@'s 4-year old patch:
https://lists.freebsd.org/pipermail/freebsd-arch/2013-July/014471.html
Reviewed by: kib, gallatin, marius, lidl
Differential Revision: https://reviews.freebsd.org/D10156
Renumber cluase 4 to 3, per what everybody else did when BSD granted
them permission to remove clause 3. My insistance on keeping the same
numbering for legal reasons is too pedantic, so give up on that point.
Submitted by: Jan Schaumann <jschauma@stevens.edu>
Pull Request: https://github.com/freebsd/freebsd/pull/96
one respect. When determining how many page structures to allocate,
contrary to what the comments say, the code does not account for the
overhead of a page structure per page of physical memory. This revision
changes the code to match the comments.
Reviewed by: kib, markj
MFC after: 6 weeks
Differential Revision: https://reviews.freebsd.org/D9081
vm_object_madvise() is frequently used to apply advice to a contiguous
set of pages in an object with no backing object. Optimize this case by
skipping non-resident subranges in constant time, and by iterating over
resident pages using the object memq, thus avoiding radix tree lookups on
each page index in the specified range.
While here, move MADV_WILLNEED handling to vm_page_advise(), and rename the
"advise" parameter to vm_object_madvise() to "advice."
Reviewed by: alc, kib
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D9098
On systems without a configured swap device, an attempt to launder pages
from a swap object will always fail and result in the page being
reactivated. This means that the page daemon will continuously scan pages
that can never be evicted. With this change, anonymous pages are instead
moved to PQ_UNSWAPPABLE after a failed laundering attempt when no swap
devices are configured. PQ_UNSWAPPABLE is not scanned unless a swap device
is configured, so unreferenced unswappable pages are excluded from the page
daemon's workload.
Reviewed by: alc
add support for object types that were previously prohibited because they
could contain PG_CACHED pages.
Roughly halve the number of radix trie operations performed by
vm_page_alloc_contig() using the same approach that is employed by
vm_page_alloc(). Also, eliminate the radix trie lookup performed with the
free page queues lock held.
Tidy up the handling of radix trie insert failures in vm_page_alloc() and
vm_page_alloc_contig().
Reviewed by: kib, markj
Tested by: pho
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D8878
independent layer of the virtual memory system. Update some of the nearby
comments to eliminate redundancy and improve clarity.
In vm/vm_reserv.c, do not use hyphens after adverbs ending in -ly per
The Chicago Manual of Style.
Update the comment in vm/vm_page.h defining the four types of page queues to
reflect the elimination of PG_CACHED pages and the introduction of the
laundry queue.
Reviewed by: kib, markj
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D8752
contain a vm_page_t at the specified index. However, with this
change, vm_radix_remove() no longer panics. Instead, it returns NULL
if there is no vm_page_t at the specified index. Otherwise, it
returns the vm_page_t. The motivation for this change is that it
simplifies the use of radix tries in the amd64, arm64, and i386 pmap
implementations. Instead of performing a lookup before every remove,
the pmap can simply perform the remove.
Reviewed by: kib, markj
Differential Revision: https://reviews.freebsd.org/D8708
a new page of radix trie nodes to complete a vm_radix_insert() operation
that was requested by vm_page_cache(). Specifically, vm_page_cache()
already held the free page queue lock when UMA tried to acquire it through
a call to vm_page_alloc(). This code path no longer exists, so there is no
longer any reason to allow recursion on the free page queue mutex.
Improve nearby comments.
Reviewed by: kib, markj
Tested by: pho
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D8628
longer used. More precisely, they are always zero because the code that
decremented and incremented them no longer exists.
Bump __FreeBSD_version to mark this change.
Reviewed by: kib, markj
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D8583
not remove user-space visible fields from vm_cnt or all of the references to
cached pages from comments. Those changes will come later.)
Reviewed by: kib, markj
Tested by: pho
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D8497
pages, specificially, dirty pages that have passed once through the inactive
queue. A new, dedicated thread is responsible for both deciding when to
launder pages and actually laundering them. The new policy uses the
relative sizes of the inactive and laundry queues to determine whether to
launder pages at a given point in time. In general, this leads to more
intelligent swapping behavior, since the laundry thread will avoid pageouts
when the marginal benefit of doing so is low. Previously, without a
dedicated queue for dirty pages, the page daemon didn't have the information
to determine whether pageout provides any benefit to the system. Thus, the
previous policy often resulted in small but steadily increasing amounts of
swap usage when the system is under memory pressure, even when the inactive
queue consisted mostly of clean pages. This change addresses that issue,
and also paves the way for some future virtual memory system improvements by
removing the last source of object-cached clean pages, i.e., PG_CACHE pages.
The new laundry thread sleeps while waiting for a request from the page
daemon thread(s). A request is raised by setting the variable
vm_laundry_request and waking the laundry thread. We request launderings
for two reasons: to try and balance the inactive and laundry queue sizes
("background laundering"), and to quickly make up for a shortage of free
pages and clean inactive pages ("shortfall laundering"). When background
laundering is requested, the laundry thread computes the number of page
daemon wakeups that have taken place since the last laundering. If this
number is large enough relative to the ratio of the laundry and (global)
inactive queue sizes, we will launder vm_background_launder_target pages at
vm_background_launder_rate KB/s. Otherwise, the laundry thread goes back
to sleep without doing any work. When scanning the laundry queue during
background laundering, reactivated pages are counted towards the laundry
thread's target.
In contrast, shortfall laundering is requested when an inactive queue scan
fails to meet its target. In this case, the laundry thread attempts to
launder enough pages to meet v_free_target within 0.5s, which is the
inactive queue scan period.
A laundry request can be latched while another is currently being
serviced. In particular, a shortfall request will immediately preempt a
background laundering.
This change also redefines the meaning of vm_cnt.v_reactivated and removes
the functions vm_page_cache() and vm_page_try_to_cache(). The new meaning
of vm_cnt.v_reactivated now better reflects its name. It represents the
number of inactive or laundry pages that are returned to the active queue
on account of a reference.
In collaboration with: markj
Reviewed by: kib
Tested by: pho
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D8302
Requests which cannot be satisfied by allocators at boot time often
have unrealizable parameters. Waiting for the pagedaemon' start would
hang the boot if done in the thread0 context and just never succeed if
executed from another thread. In fact, for very early stages, sleep
attempt panics with obscure diagnostic about the scheduler state, and
explicit panic in vm_wait() makes the investigation much shorter by
cut off the examination of the thread and scheduler.
Theoretically, some subsystem might grab a resource to exhaustion, and
free it later in the boot process. If this unlikely scenario does
appear for real, the way to diagnose the trouble can be revisited.
Reported by: emaste
Reviewed by: markj
Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks
Differential revision: https://reviews.freebsd.org/D8421
Suppose that we have an exclusively busy page, and a thread which can
accept shared-busy page. In this case, typical code waiting for the
page xbusy state to pass is
again:
VM_OBJECT_WLOCK(object);
...
if (vm_page_xbusied(m)) {
vm_page_lock(m);
VM_OBJECT_WUNLOCK(object); <---1
vm_page_busy_sleep(p, "vmopax");
goto again;
}
Suppose that the xbusy state owner locked the object, unbusied the
page and unlocked the object after we are at the line [1], but before we
executed the load of the busy_lock word in vm_page_busy_sleep(). If it
happens that there is still no waiters recorded for the busy state,
the xbusy owner did not acquired the page lock, so it proceeded.
More, suppose that some other thread happen to share-busy the page
after xbusy state was relinquished but before the m->busy_lock is read
in vm_page_busy_sleep(). Again, that thread only needs vm_object lock
to proceed. Then, vm_page_busy_sleep() reads busy_lock value equal to
the VPB_SHARERS_WORD(1).
In this case, all tests in vm_page_busy_sleep(9) pass and we are going
to sleep, despite the page being share-busied.
Update check for m->busy_lock == VPB_UNBUSIED in vm_page_busy_sleep(9)
to also accept shared-busy state if we only wait for the xbusy state to
pass.
Merge sequential if()s with the same 'then' clause in
vm_page_busy_sleep().
Note that the current code does not share-busy pages from parallel
threads, the only way to have more that one sbusy owner is right now
is to recurse.
Reported and tested by: pho (previous version)
Reviewed by: alc, markj
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D8196
waiters. Otherwise, owners of the shared-busy state are left blocked
and might get into a deadlock.
Note that the vm_page_busy_downgrade() function is not used in the
tree right now.
Reported and tested by: pho (previous version)
Reviewed by: alc, markj
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D8195
by vm_pageout_scan() local to vm_pageout_worker(). There is no reason
to store the pass in the NUMA domain structure.
Reviewed by: kib
MFC after: 3 weeks
Idle page zeroing has been disabled by default on all architectures since
r170816 and has some bugs that make it seemingly unusable. Specifically,
the idle-priority pagezero thread exacerbates contention for the free page
lock, and yields the CPU without releasing it in non-preemptive kernels. The
pagezero thread also does not behave correctly when superpage reservations
are enabled: its target is a function of v_free_count, which includes
reserved-but-free pages, but it is only able to zero pages belonging to the
physical memory allocator.
Reviewed by: alc, imp, kib
Differential Revision: https://reviews.freebsd.org/D7714
The removal of vm_fault_additional_pages() meant that a hard fault on
a swap-backed page would result in only that page being read in. This
change implements readahead and readbehind for the swap pager in
swap_pager_getpages(). swap_pager_haspage() is modified to return the
largest contiguous non-resident range of pages containing the requested
range.
Reviewed by: alc, kib
Tested by: pho
MFC after: 1 month
Differential Revision: https://reviews.freebsd.org/D7677
of CPUs present. On amd64 this unbreaks the boot for systems with 92 or
more CPUs; the limit will vary on other systems depending on the size of
their uma_zone and uma_cache structures.
The major consumer of pages during UMA startup is the 19 zone structures
which are set up before UMA has bootstrapped itself sufficiently to use
the rest of the available memory: UMA Slabs, UMA Hash, 4 / 6 / 8 / 12 /
16 / 32 / 64 / 128 / 256 Bucket, vmem btag, VM OBJECT, RADIX NODE, MAP,
KMAP ENTRY, MAP ENTRY, VMSPACE, and fakepg. If the zone structures occupy
more than one page, they will not share pages and the number of pages
currently needed for startup is 19 * pages_per_zone + N, where N is the
number of pages used for allocating other structures; on amd64 N = 3 at
present (2 pages are allocated for UMA Kegs, and one page for UMA Hash).
This patch adds a new definition UMA_BOOT_PAGES_ZONES, currently set to 32,
and if a zone structure does not fit into a single page sets boot_pages to
UMA_BOOT_PAGES_ZONES * pages_per_zone instead of UMA_BOOT_PAGES (which
remains at 64). Consequently this patch has no effect on systems where the
zone structure fits into 2 or fewer pages (on amd64, 59 or fewer CPUs), but
increases boot_pages sufficiently on systems where the large number of CPUs
makes this structure larger. It seems safe to assume that systems with 60+
CPUs can afford to set aside an additional 128kB of memory per 32 CPUs.
The vm.boot_pages tunable continues to override this computation, but is
unlikely to be necessary in the future.
Tested on: EC2 x1.32xlarge
Relnotes: FreeBSD can now boot on 92+ CPU systems without requiring
vm.boot_pages to be manually adjusted.
Reviewed by: jeff, alc, adrian
Approved by: re (kib)
waiters exist, same as for vm_page_xunbusy(). If previous value of
busy_lock was VPB_SINGLE_EXCLUSIVER, no waiters existed and wakeup is
not needed.
Move common code from vm_page_xunbusy_maybelocked() and
vm_page_xunbusy_hard() to vm_page_xunbusy_locked().
Reviewed by: alc
Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks
Approved by: re (gjb)
Per the KASSERT at the beginning of the function, we expect that the page
does not belong to any object, so its object and pindex fields are
meaningless. Reset them in the rare case that vm_radix_insert() fails.
Reviewed by: kib
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D6669
acquire the page lock, which recurses. Avoid the recursion by reusing
the code from vm_page_remove() in a new helper
vm_page_xunbusy_maybelocked().
Reviewed by: alc
Sponsored by: The FreeBSD Foundation
indicate that threads are waiting for free pages to become available and
(2) to indicate whether a wakeup call has been sent to the page daemon.
The trouble is that a single flag cannot really serve both purposes, because
we have two distinct targets for when to wakeup threads waiting for free
pages versus when the page daemon has completed its work. In particular,
the flag will be cleared by vm_page_free() before the page daemon has met
its target, and this can lead to the OOM killer being invoked prematurely.
To address this problem, a new flag "vm_pageout_wanted" is introduced.
Discussed with: jeff
Reviewed by: kib, markj
Tested by: markj
Sponsored by: EMC / Isilon Storage Division
for empty page cache when the object type if OBJT_VNODE.
Reported and tested by: pho
Reviewed by: alc
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
freed page as VPO_UNMANAGED. Otherwise vm_pge_free_toq() insists on
owning the page lock.
Previously, VPO_UNMANAGED was only set up to the last processed page.
Reviewed by: alc
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
pq_vcnt, as a count of real things, has no business being negative. It is only
ever initialized by a u_int counter.
The warning came from the atomic_add_int() in vm_pagequeue_cnt_add().
Rectify the warning by changing the variable to u_int. No functional change.
Suggested by: Clang 3.3
Sponsored by: EMC / Isilon Storage Division
rounddown2 tends to produce longer lines than the original code
and when the code has a high indentation level it was not really
advantageous to do the replacement.
This tries to strike a balance between readability using the macros
and flexibility of having the expressions, so not everything is
converted.
address and use this mechanism when:
1. kmem_alloc_{attr,contig}() can't find suitable free pages in the physical
memory allocator's free page lists. This replaces the long-standing
approach of scanning the inactive and inactive queues, converting clean
pages into PG_CACHED pages and laundering dirty pages. In contrast, the
new mechanism does not use PG_CACHED pages nor does it trigger a large
number of I/O operations.
2. on 32-bit MIPS processors, uma_small_alloc() and the pmap can't find
free pages in the physical memory allocator's free page lists that are
covered by the direct map. Tested by: adrian
3. ttm_bo_global_init() and ttm_vm_page_alloc_dma32() can't find suitable
free pages in the physical memory allocator's free page lists.
In the coming months, I expect that this new mechanism will be applied in
other places. For example, balloon drivers should use relocation to
minimize fragmentation of the guest physical address space.
Make vm_phys_alloc_contig() a little smarter (and more efficient in some
cases). Specifically, use vm_phys_segs[] earlier to avoid scanning free
page lists that can't possibly contain suitable pages.
Reviewed by: kib, markj
Glanced at: jhb
Discussed with: jeff
Sponsored by: EMC / Isilon Storage Division
Differential Revision: https://reviews.freebsd.org/D4444
o With new KPI consumers can request contiguous ranges of pages, and
unlike before, all pages will be kept busied on return, like it was
done before with the 'reqpage' only. Now the reqpage goes away. With
new interface it is easier to implement code protected from race
conditions.
Such arrayed requests for now should be preceeded by a call to
vm_pager_haspage() to make sure that request is possible. This
could be improved later, making vm_pager_haspage() obsolete.
Strenghtening the promises on the business of the array of pages
allows us to remove such hacks as swp_pager_free_nrpage() and
vm_pager_free_nonreq().
o New KPI accepts two integer pointers that may optionally point at
values for read ahead and read behind, that a pager may do, if it
can. These pages are completely owned by pager, and not controlled
by the caller.
This shifts the UFS-specific readahead logic from vm_fault.c, which
should be file system agnostic, into vnode_pager.c. It also removes
one VOP_BMAP() request per hard fault.
Discussed with: kib, alc, jeff, scottl
Sponsored by: Nginx, Inc.
Sponsored by: Netflix
Remove redundant lookup of the old page from vm_page_replace. Verification
that the old page exists is already done by vm_radix_replace.
Submitted by: Ryan Libby <rlibby@gmail.com>
Reviewed by: alc, kib
Sponsored by: EMC / Isilon Storage Division
Follow-up to: https://reviews.freebsd.org/D4326
Differential Revision: https://reviews.freebsd.org/D4471
reclaimed in FIFO order by the pagedaemon. Previously we would enqueue
such pages at the head of the inactive queue, yielding a LIFO reclaim order.
Reviewed by: alc
MFC after: 2 weeks
Sponsored by: EMC / Isilon Storage Division
of POSIX_FADV_DONTNEED so that it causes the backing pages to be moved to
the head of the inactive queue instead of being cached.
This affects the implementation of POSIX_FADV_NOREUSE as well, since it
works by applying POSIX_FADV_DONTNEED to file ranges after they have been
read or written. At that point the corresponding buffers may still be
dirty, so the previous implementation would coalesce successive ranges and
apply POSIX_FADV_DONTNEED to the result, ensuring that pages backing the
dirty buffers would eventually be cached. To preserve this behaviour in an
efficient manner, this change adds a new buf flag, B_NOREUSE, which causes
the pages backing a VMIO buf to be placed at the head of the inactive queue
when the buf is released. POSIX_FADV_NOREUSE then works by setting this
flag in bufs that underlie the specified range.
Reviewed by: alc, kib
Sponsored by: EMC / Isilon Storage Division
Differential Revision: https://reviews.freebsd.org/D3726
queue and (2) returns a Boolean indicating whether the page's wire count
transitioned to zero.
Exploit this change in vfs_vmio_release() to avoid pointlessly enqueueing
a page that is about to be freed.
(An earlier version of this change was developed by attilio@ and kmacy@.
Any errors in this version are my own.)
Reviewed by: kib
Sponsored by: EMC / Isilon Storage Division
with a reference count of zero can't possibly be mapped, so there is never a
need for vm_page_set_invalid() to call pmap_remove_all() on them.
Reviewed by: kib
MFC after: 1 week
Sponsored by: EMC / Isilon Storage Division
This was added in r51337 as part of the implementation of
madvise(MADV_DONTNEED). Its objective was to ensure that the page daemon
would eventually reclaim other unreferenced pages (i.e., unreferenced pages
not touched by madvise()) from the active queue.
Now that the pagedaemon performs steady scanning of the active page queue,
this weighted handling is unnecessary. Instead, always "cache" clean pages
by moving them to the head of the inactive page queue. This simplifies the
implementation of vm_page_advise() and eliminates the fragmentation that
resulted from the distribution of pages among multiple queues.
Suggested by: alc
Reviewed by: alc
Sponsored by: EMC / Isilon Storage Division
Differential Revision: https://reviews.freebsd.org/D3401
r283162.
Fix a cosmetic issue with vm_page_alloc() calling vm_page_free_toq()
with the page not completely satisfying vm_page_free() assertions.
The page is not owned by the object, since insertion failed. But
besides m->object reset to NULL, we should also set VPO_UNMANAGED flag
for consistency.
Reported by: pho
Reviewed by: alc
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
