* Made the page table allocation more flexible. Got rid of sMaxVirtualAddress
and added new virtual_end address to the architecture specific kernel args.
* Increased the virtual space we reserve for the kernel to 16 MB. That
should suffice for quite a while. The previous 2 MB were too tight when
building the kernel with debug info.
* mmu_init(): The way we were translating the BIOS' extended memory map to
our physical ranges arrays was broken. Small gaps between usable memory
ranges would be ignored and instead marked allocated. This worked fine for
the boot loader and during the early kernel initialization, but after the
VM has been fully set up it frees all physical ranges that have not been
claimed otherwise. So those ranges could be entered into the free pages
list and would be used later. This could possibly cause all kinds of weird
problems, probably including ACPI issues. Now we add only the actually
usable ranges to our list.
Kernel:
* vm_page_init(): The pages of the ranges between the usable physical memory
ranges are now marked PAGE_STATE_UNUSED, the allocated ranges
PAGE_STATE_WIRED.
* unmap_and_free_physical_pages(): Don't free pages marked as unused.
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happen on syscalls or "int" instructions. The debug exception handler sets
the thread debug flags B_THREAD_DEBUG_STOP and
B_THREAD_DEBUG_NOTIFY_SINGLE_STEP (new) and lets the thread continue. Before
leaving the kernel the thread is stopped and a single-step notification is
sent. Fixes#3487.
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over ownership of the object. Fixes double free introduced in r35605.
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they were never freed unless the cache was destroyed (I just wondered why
my system would bury >1G in the magazines).
* Made the magazine capacity variable per cache, ie. for larger objects, it's
not a good idea to have 64*CPU buffers lying around in the worst case.
* Furthermore, the create_object_cache_etc()/object_depot_init() now have
arguments for the magazine capacity as well as the maximum number of full
unused magazines.
* By default, you might want to initialize both to zero, as then some hopefully
usable defaults are computed. Otherwise (the only current example is the
vm_page_mapping cache) you can just put in the values you'd want there.
The page mapping cache uses larger values, as its objects are usually
allocated and deleted in larger chunks.
* Beware, though, I couldn't test these changes yet as Qemu didn't like to run
today. I'll test these changes on another machine now.
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needs to be or'ed to the address specification), "uncached" is assumed.
* Set the memory type for the "BIOS" and "DMA" areas to write-back. Not sure, if
that's correct, but that's what was effectively used on my machines before.
* Changed x86_set_mtrrs() and the CPU module hook to also set the default memory
type.
* Rewrote the MTRR computation once more:
- Now we know all used memory ranges, so we are free to extend used ranges
into unused ones in order to simplify them for MTRR setup.
- Leverage the subtractive properties of uncached and write-through ranges to
simplify ranges of any other respectively write-back type.
- Set the default memory type to write-back, so we don't need MTRRs for the
RAM ranges.
- If a new range intersects with an existing one, we no longer just fail.
Instead we use the strictest requirements implied by the ranges. This fixes
#5383.
Overall the new algorithm should be sufficient with far less MTRRs than before
(on my desktop machine 4 are used at maximum, while 8 didn't quite suffice
before). A drawback of the current implementation is that it doesn't deal with
the case of running out of MTRRs at all, which might result in some ranges
having weaker caching/memory ordering properties than requested.
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* Added vm_clear_page_mapping_accessed_flags() and
vm_remove_all_page_mappings_if_unaccessed(), which combine the functionality
of vm_test_map_activation(), vm_clear_map_flags(), and
vm_remove_all_page_mappings(), thus saving lots of calls to translation map
methods. The backend is the new method
VMTranslationMap::ClearAccessedAndModified().
* Started to make use of the cached page queue and changed the meaning of the
other non-free queues slightly:
- Active queue: Contains mapped pages that have been used recently.
- Inactive queue: Contains mapped pages that have not been used recently. Also
contains unmapped temporary pages.
- Modified queue: Contains unmapped modified pages.
- Cached queue: Contains unmapped unmodified pages (LRU sorted).
Unless we're actually low on memory and actively do paging, modified and
cached queues only contain non-temporary pages. Cached pages are considered
quasi free. They still belong to a cache, but since they are unmodified and
unmapped, they can be freed immediately. And this is what
vm_page_[try_]reserve_pages() do now when there are no more actually free
pages at hand. Essentially this means that pages storing cached file data,
unless mmap()ped, no longer are considered used and don't contribute to page
pressure. Paging will not happen as long there are enough free + cached pages
available.
* Reimplemented the page daemon. It no longer scans all pages, but instead works
the page queues. As long as the free pages situation is harmless, it only
iterates through the active queue and deactivates pages that have not been
used recently. When paging occurs it additionally scans the inactive queue and
frees pages that have not been used recently.
* Changed the page reservation/allocation interface:
vm_page_[try_]reserve_pages(), vm_page_unreserve_pages(), and
vm_page_allocate_page() now take a vm_page_reservation structure pointer.
The reservation functions initialize the structure -- currently consisting
only of a count member for the number of still reserved pages.
vm_page_allocate_page() decrements the count and vm_page_unreserve_pages()
unreserves the remaining pages (if any). Advantages are that reservation/
unreservation mismatches cannot occur anymore, that vm_page_allocate_page()
can verify that the caller has indeed a reserved page left, and that there's
no unnecessary pressure on the free page pool anymore. The only disadvantage
is that the vm_page_reservation object needs to be passed around a bit.
* Reworked the page reservation implementation:
- Got rid of sSystemReservedPages and sPageDeficit. Instead
sUnreservedFreePages now actually contains the number of free pages that
have not yet been reserved (it cannot become negative anymore) and the new
sUnsatisfiedPageReservations contains the number of pages that are still
needed for reservation.
- Threads waiting for reservations do now add themselves to a waiter queue,
which is ordered by descending priority (VM priority and thread priority).
High priority waiters are served first when pages become available.
Fixes#5328.
* cache_prefetch_vnode(): Would reserve one less page than allocated later, if
the size wasn't page aligned.
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general "flags" parameter. It encodes the target state of the page -- so
that the page isn't unnecessarily put in the wrong page queue first -- a
flag whether the page should be cleared, and one to indicate whether the
page should be marked busy.
* Added page state PAGE_STATE_CACHED. Not used yet.
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flag. The obvious advantage is that one can still see what state a page is in
and even move it between states while being marked busy.
* Removed the vm_page::is_dummy flag. Instead we mark marker pages busy, which
in all cases has the same effect. Introduced a vm_page_is_dummy() that can
still check whether a given page is a dummy page.
* vm_page_unreserve_pages(): Before adding to the system reserve make sure
sUnreservedFreePages is non-negative. Otherwise we'd make nonexisting pages
available for allocation. steal_pages() still has the same problem and it
can't be solved that easily.
* map_page(): No longer changes the page state/mark the page unbusy. That's the
caller's responsibility.
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argument. They replace the previous special-purpose allocation functions
(malloc_nogrow(), vip_io_request_malloc()).
* Moved the I/O VIP heap to heap.cpp accordingly.
* Added quite a bit of passing around of allocation flags in the VM,
particularly in the VM*AddressSpace classes.
* Fixed IOBuffer::GetNextVirtualVec(): It was ignoring the VIP flag and always
allocated on the normal heap.
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memory and page reservation functions have a new "priority" parameter that
indicates how deep the function may tap into that reserve. The currently
existing priority levels are "user", "system", and "VIP". The idea is that
user programs should never be able to cause a state that gets the kernel into
trouble due to heavy battling for memory. The "VIP" level (not really used
yet) is intended for allocations that are required to free memory eventually
(in the page writer). More levels are thinkable in the future, like "user real
time" or "user system server".
* Added "priority" parameters to several VMCache methods.
* Replaced the map_backing_store() "unmapAddressRange" parameter by a "flags"
parameter.
* Added area creation flag CREATE_AREA_PRIORITY_VIP and slab allocator flag
CACHE_PRIORITY_VIP indicating the importance of the request.
* Changed most code to pass the right priorities/flags.
These changes already significantly improve the behavior in low memory
situations. I've tested a bit with 64 MB (virtual) RAM and, while not
particularly fast and responsive, the system remains at least usable under high
memory pressure.
As a side effect the slab allocator can now be used as general memory allocator.
Not done by default yet, though.
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* Added support to do larger raw allocations (up to one large chunk (128 pages))
in the slab areas. For an even larger allocation an area is created (haven't
seen that happen yet, though).
* Added kernel tracing (SLAB_MEMORY_MANAGER_TRACING).
* _FreeArea(): Copy and paste bug: The meta chunks of the to be freed area
would be added to the free lists instead of being removed from them. This
would corrupt the lists and also lead to all kinds of misuse of meta chunks.
object caches:
* Implemented CACHE_ALIGN_ON_SIZE. It is no longer set for all small object
caches, but the block allocator sets it on all power of two size caches.
* object_cache_reserve_internal(): Detect recursion and don't wait in such a
case. The function could deadlock itself, since
HashedObjectCache::CreateSlab() does allocate memory, thus potentially
reentering.
* object_cache_low_memory():
- I missed some returns when reworking that one in r35254, so the function
might stop early and also leave the cache in maintenance mode, which would
cause it to be ignored by object cache resizer and low memory handler from
that point on.
- Since ReturnSlab() potentially unlocks, the conditions weren't quite correct
and too many slabs could be freed.
- Simplified things a bit.
* object_cache_alloc(): Since object_cache_reserve_internal() does potentially
unlock the cache, the situation might have changed and their might not be an
empty slab available, but a partial one. The function would crash.
* Renamed the object cache tracing variable to SLAB_OBJECT_CACHE_TRACING.
* Renamed debugger command "cache_info" to "slab_cache" to avoid confusion with
the VMCache commands.
* ObjectCache::usage was not maintained anymore since I introduced the
MemoryManager. object_cache_get_usage() would thus always return 0 and the
block cache would not be considered cached memory. This was only of
informational relevance, though.
slab allocator misc.:
* Disable the object depots of block allocator caches for object sizes > 2 KB.
Allocations of those sizes aren't so common that the object depots yield any
benefit.
* The slab allocator is now fully self-sufficient. It allocates its bootstrap
memory from the MemoryManager, and the hash tables for HashedObjectCaches use
the block allocator instead of the heap, now.
* Added option to use the slab allocator for malloc() and friends
(USE_SLAB_ALLOCATOR_FOR_MALLOC). Currently disabled. Works in principle and
has virtually no lock contention. Handling for low memory situations is yet
missing, though.
* Improved the output of some debugger commands.
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* Added optional parameter "void** oldTable" to Resize(). If given the old
allocation for the table is returned instead of freeing it.
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CACHE_DONT_LOCK_KERNEL_SPACE. If the former is given, the slab memory manager
does not wait when reserving memory or pages. The latter prevents area
operations. The new flags add a bit of flexibility. E.g. when allocating page
mapping objects for userland areas CACHE_DONT_WAIT_FOR_MEMORY is sufficient,
i.e. the allocation will succeed as long as pages are available.
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* Implemented a more elaborated raw memory allocation backend (MemoryManager).
We allocate 8 MB areas whose pages we allocate and map when needed. An area is
divided into equally-sized chunks which form the basic units of allocation. We
have areas with three possible chunk sizes (small, medium, large), which is
basically what the ObjectCache implementations were using anyway.
* Added "uint32 flags" parameter to several of the slab allocator's object
cache and object depot functions. E.g. object_depot_store() potentially wants
to allocate memory for a magazine. But also in pure freeing functions it
might eventually become useful to have those flags, since they could end up
deleting an area, which might not be allowable in all situations. We should
introduce specific flags to indicate that.
* Reworked the block allocator. Since the MemoryManager allocates block-aligned
areas, maintains a hash table for lookup, and maps chunks to object caches,
we can quickly find out which object cache a to be freed allocation belongs
to and thus don't need the boundary tags anymore.
* Reworked the slab boot strap process. We allocate from the initial area only
when really necessary, i.e. when the object cache for the respective
allocation size has not been created yet. A single page is thus sufficient.
other:
* vm_allocate_early(): Added boolean "blockAlign" parameter. If true, the
semantics is the same as for B_ANY_KERNEL_BLOCK_ADDRESS.
* Use an object cache for page mappings. This significantly reduces the
contention on the heap bin locks.
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one for each per CPU store):
* The depot is now protected by a R/W lock combined with a spinlock. It is
required to either hold read lock + spinlock or just the write lock.
* When accessing the per CPU stores we only need to acquire the read lock
and disable interrupts. When switching magazines with the depot we
additionally get the spinlock.
* When allocating a new magazine we do completely unlock.
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* The threads beside the main thread are killed earlier now (in the new
team_shutdown_team()), before removing the team from the team hash and from
its process group. This fixes#5296.
* Use a condition variable instead of a semaphore to wait for the non-main
threads to die. We notify the condition right after a thread has left the
team. The semaphore was released by the undertaker.
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things a bit.
* Some style cleanup.
* The object depot does now have a cookie that will be passed to the return
hook.
* Fixed object_cache_return_object_wrapper() using the new cookie.
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VMCacheRef object which points to the cache. This allows to optimize
VMCache::MoveAllPages(), since it no longer needs to iterate over all pages
to adjust their cache pointer. It can simple swap the cache refs of the two
caches instead.
Reduces the total -j8 Haiku image build time only marginally. The kernel time
drops almost 10%, though.
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* Added "bool consumerLocked" parameter to VMCache::Unlock() and
ReleaseRefAndUnlock(). Since Unlock() may cause the cache to be merged with
a consumer cache, the flag is needed to prevent a deadlock in case the
caller still holds a lock to the consumer. Hasn't been a problem yet, since
that situation never occurred.
* VMCacheChainLocker: Reversed unlocking order to bottom-up. The other
direction could cause a deadlock in case caches would be merged, since the
locking order would be reversed. The way VMCacheChainLocker was used this
didn't happen, though.
* fault_get_page(): While copying a page from a lower cache to the top cache,
we do now unlock all caches but the top one, so we don't unnecessarily
kill concurrency.
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* Reorganized the code for [un]mapping pages:
- Added new VMTranslationMap::Unmap{Area,Page[s]}() which essentially do what
vm_unmap_page[s]() did before, just in the architecture specific code, which
allows for specific optimizations. UnmapArea() is for the special case that
the complete area is unmapped. Particularly in case the address space is
deleted, some work can be saved. Several TODOs could be slain.
- Since they are only used within vm.cpp vm_map_page() and vm_unmap_page[s]()
are now static and have lost their prefix (and the "preserveModified"
parameter).
* Added VMTranslationMap::Protect{Page,Area}(). They are just inline wrappers
for Protect().
* X86VMTranslationMap::Protect(): Make sure not to accidentally clear the
accessed/dirty flags.
* X86VMTranslationMap::Unmap()/Protect(): Make page table skipping actually
work. It was only skipping to the next page.
* Adjusted the PPC code to at least compile.
No measurable effect for the -j8 Haiku image build time, though the kernel time
drops minimally.
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* Pulled the physical page mapping functions out of vm_translation_map into
a new interface VMPhysicalPageMapper.
* Renamed vm_translation_map to VMTranslationMap and made it a proper C++
class. The functions in the operations vector have become methods.
* Added class GenericVMPhysicalPageMapper implementing VMPhysicalPageMapper
as far as possible (without actually writing new code).
* Adjusted the x86 and the PPC specifics accordingly (untested for the
latter). For the other architectures the build is, I'm afraid, seriously
broken.
The next steps will modify and extend the VMTranslationMap interface, so that
it will be possible to fix the bugs in vm_unmap_page[s]() and employ
architecture specific optimizations.
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* ioapic_init(): map_physical_memory() was called for already mapped
addresses. This worked fine, but only because the x86 page mapping code
didn't mind.
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* Use atomic_{and,or}() instead of atomic_set(), as there are no built-ins
for the latter.
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This makes appending the pages to the active queue more efficient and we
don't need the vm_page::is_cleared bit anymore.
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* Added Debug{First,Next}() methods to allow easy iteration through the
address spaces in kernel debugger commands.
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device path + child partition name. When a "raw" device is unpublished the node
removal notification triggers the partition and child partitions to be
unpublished/removed. Since in that case the "raw" node is already unpublished
trying to resolve it in devfs_unpublish_partition() again to unpublish the child
partitions would fail, leaving the child partition nodes behind. When a new raw
device would then become available publishing its partitions would fail because
of these left behind nodes, causing bug #4587. Seeing that this code is more
compact and straight forward anyway I don't quite see why it was changed in the
first place.
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table. It is now inline and uses double-checked locking. This reduces the
contention on the lock to insignificant. Total -j8 Haiku image build speedup
is marginal, but the total kernel time drops 12%.
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access to a vm_page. It is basically an atomically accessed thread ID field
in the vm_page structure, which is explicitly set by macros marking the
critical sections. As a first positive effect I had to review quite a bit of
code and found several issues.
* Added several TODOs and comments. Some harmless ones, but also a few
troublesome ones in vm.cpp regarding page unmapping.
* file_cache: PrecacheIO::Prepare()/read_into_cache: Removed superfluous
vm_page_allocate_page() return value checks. It cannot fail anymore.
* Removed the heavily contended "pages" lock. We use different policies now:
- sModifiedTemporaryPages is accessed atomically.
- sPageDeficitLock and sFreePageCondition are protected by a new mutex.
- The page queues have individual locks (mutexes).
- Renamed set_page_state_nolock() to set_page_state(). Unless the caller says
otherwise, it does now lock the affected pages queues itself. Also changed
the return value to void -- we panic() anyway.
* set_page_state(): Add free/clear pages to the beginning of their respective
queues as this is more cache-friendly.
* Pages with the states PAGE_STATE_WIRED or PAGE_STATE_UNUSED are no longer
in any queue. They were in the "active" queue, but there's no good reason
to have them there. In case we decide to let the page daemon work the queues
(like FreeBSD) they would just be in the way.
* Pulled the common part of vm_page_allocate_page_run[_no_base]() into a helper
function. Also fixed a bug I introduced previously: The functions must not
vm_page_unreserve_pages() on success, since they remove the pages from the
free/clear queue without decrementing sUnreservedFreePages.
* vm_page_set_state(): Changed return type to void. The function cannot really
fail and no-one was checking it anyway.
* vm_page_free(), vm_page_set_state(): Added assertion: The page must not be
free/clear before. This is implied by the policy that no-one is allowed to
access free/clear pages without holding the respective queue's lock, which is
not the case at this point. This found the bug fixed in r34912.
* vm_page_requeue(): Added general assertions. panic() when requeuing of
free/clear pages is requested. Same reason as above.
* vm_clone_area(), B_FULL_LOCK case: Don't map busy pages. The implementation is
still not correct, though.
My usual -j8 Haiku build test runs another 10% faster, now. The total kernel
time drops about 18%. As hoped the new locks have only a fraction of the old
"pages" lock contention. Other locks lead the "most wanted list" now.
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* Renamed page_queue to VMPageQueue and made it a proper C++ class. Use
DoublyLinkedList instead of own list code.
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have one anymore anyway.
* Removed unnecessary setting the list links to NULL after removing a node.
* Replaced "element == NULL" check in Insert() by an assert. This just hid
potential errors.
* Added Insert{Before,After}() methods and declared the Insert() version
with the InsertBefore() semantics obsolete.
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