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.
