keeping all returned heap memory in the 0xdeadbeef state (including the
first sizeof(void *) bytes otherwise for the free list). While wasting a lot
of memory it allows you to rely on 0xdeadbeef being always present as no
future allocation will reuse the freed memory block.
* Also added heap_debug_malloc_with_guard_page() which is intended to allocate
a memory block so it is aligned that the start of invalid memory past the
allocation is in an unmapped guard page. However the kernel backend that would
guarantee this is not yet implemented, so right now this works only by chance
if no other area happens to be allocated exactly past the created one. With a
very specifc suspicion you can put that one allocation you get to good use
though. It causes a crash when accessing memory past the allocation size so
you actually get a backtrace from where the access happened instead of only
after freeing/wall checking.
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it has been unmapped. This way modified pages could end up in the "cached"
queue without having been written back. That would be a good explanation for
#5374 (partially wrong file contents) -- as soon as such a page was freed,
the invalid on-disk contents would become visible.
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so the fallback implementations of UnmapPages() and UnmapArea() need to do
that. Not relevant for x86.
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though).
* Added/improved some KDL commands to make the slab easier to work with from
KDL.
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* Renamed the "busy" stuff to "busy_reading", and added a "busy_writing"
concept.
* This now allows reading a block (and other blocks), while blocks are written
back. This should speed all operations needing to write back blocks, like
unzipping or compiling.
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driver_events (ie. there is now only a single list to walk).
* Also, the DriverWatcher is now maintained using the driver_events.
This fixes bug #5005.
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call with the true parameter. Fixes a panic at boot when using the hpet timers
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which happened on some systems (mine included).
Should close ticket #5341.
Thanks!
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* Moving some functions around, removing and adding others for the public API.
I've written a blog post at haiku-os.org to go as documentation for this
introducing the API and the other helpful bits.
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the contiguous page allocation function and unlocks a bin locker a bit earlier.
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* Make the contiguous page allocation capable of aligning the allocation
and make it more clever by checking up front if there's a chance of getting
enough pages at all, by giving up earlier if the page count can't be fit
anymore, and in the alignment case by only checking the pages which have a
valid alignment.
* If the alignment requirement is > B_PAGE_SIZE we now use page allocation
directly, because the bins aren't necesarily aligned on their size past
B_PAGE_SIZE anymore.
* When doing aligned bin allocation, calculate the aligned size up front and
choose the right heap for the allocation.
* Also when doing aligned bin allocations we not only need to round up the size
but also ensure that the bin we choose is aligned at all.
* Moved adding leak check info into it's own function.
Fixes various misalignment problems when working with alignments > B_PAGE_SIZE
or when using alignments < allocation size. Also the directly aligned page
allocations now only use up as many pages as actually required instead of
allocating based on the rounded up to align size.
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consider that when filling in the text and data ranges of the image info.
This fixes#5361 and #5351, caused by libtracker.so not finding its own
image.
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going on. I only wanted to have it in the repository in case we decide at a
later point that it is a good idea after all.
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its own source file now that the page daemon source file is gone.
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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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that does not have a transaction.
* This should fix#5340.
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releasing our reference to it. So return immediately after having done that.
Previously the _MaybeNotifyProfilerThread() that innocently lurked at the end
of the method would be invoked, playing with the dead beef.
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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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the wired count of manually mapped pages not to be decremented in
delete_area(), leading to a "pages still has mappings" panic when the slab
allocator's memory manager deleted areas.
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* Added flags to avoid notifying the busy condition variable unnecessarily.
* get_writable_cached_block(): Unlock the cache while memcpy()ing/memset()ing
the block's data. The idea is to reduce lock contention. Less effective
than I hoped, though.
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functional change (other than avoiding no-ops like subtracting 0).
* vm_page_try_reserve_pages(): Moved the kernel tracing calls from the top of
the function to the points where the reservation already succeeded.
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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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on the fly, clearing and writing it each time, we now use an iovec with 32
identical entries pointing to a clear page that we prepare once at
initialization. This speeds up clear_image in low memory situations
dramatically.
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beginning whether to pass the cache by really doesn't help when
reading/writing a huge amount of data, since a low memory situation is likely
to occur at some point during the operation. This should fix the main issue
of #3768.
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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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Those use malloc(), which obviously doesn't work before the heap is
initialized.
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table, we only enter the slab. This also saves us the link object per object.
* Removed the now useless {Prepare,Unprepare}Object() methods.
* SmallObjectCache: Unlock the cache while calling into the MemoryManager. We
need to do that to avoid an indirect violation of the CACHE_DONT_* policy.
* Simplified lower_boundary().
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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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VMCacheRef object, since that can fail, in which case the subsequently called
Delete() would use uninitialized pointers.
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to add it back to its partial list or it would be leaked.
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* Does now keep one or two empty areas around, so that even in case of
CACHE_DONT_LOCK_KERNEL_SPACE memory can be provided as long as pages are
available. The object cache maintainer thread is used to asynchronously
allocate/delete the free areas.
* Added new debugger commands "slab_meta_chunk[s]" and improved the existing
ones.
* Moved Area::chunks to MetaChunk.
* Removed unused _AllocationArea() "chunkSize" parameter.
* Fixed serious bug in _FreeChunk(): Empty meta chunks were not removed from
the partial chunk lists and could thus be used twice.
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adding the cache to the maintenance queue. Not so important but more correct.
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