picked might have changed while we were locking its cache. Might fix
#1931.
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of the resolved ToDo, but could probably be made more efficient. Instead of
transfering the area, the area is cloned into the target teams' address space
and the original is deleted. This generates a new area_id for the transfered
area (as suggested by the ToDo). Updated syscall prototypes according to the
status_t to area_id return type change.
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and pages are now kept in lists as well. This allows to return free pages once
a bin does not need them anymore. Partially filled pages are kept in a sorted
linked list so that allocation will always happen on the fullest page - this
favours having full pages and makes it more likely lightly used pages will get
completely empty so they can be returned. Generally this now goes more in the
direction of a slab allocator.
The allocation logic has been extracted, so a heap is now simply attachable to
a region of memory. This allows for multiple heaps and for dynamic growing. In
case the allocator runs out of free pages, an asynchronous growing thread is
notified to create a new area and attach a new heap to it.
By default the kernel heap is now set to 16MB and grows by 8MB each time all
heaps run full.
This should solve quite a few issues, like certain bins just claiming all pages
so that even if there is free space nothing can be allocated. Also it obviously
does aways with filling the heap page by page until it overgrows.
I think this is now a well performing and scalable allocator we can live with
for quite some time. It is well tested under emulation and real hardware and
performs as expected. If problems come up there is an extensive sanity checker
that can be enabled by PARANOID_VALIDATION that covers most aspects of the
allocator. For normal operation this is not necessary though and is therefore
disabled by default.
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function has the old behavior. When false, it just calls the scheduler
without any priority adjustment or other stuff.
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before releasing our cache reference. Otherwise removing a vnode (triggered
by releasing the cache in our thread) could need pages we still own.
* Put the caches and pages into a union to save stack space; they are not
needed at the same time.
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* As a temporary work-around for the current slab allocator's area usage,
I added the CACHE_LARGE_SLAB flag, which will force the allocator to
use larger areas.
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value greater or equal its size (actually untested, but at least Haiku
still boots with these changes :-)).
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* with 1 GB or more, the semaphore limit is now 131072 instead of 65536.
* double the heap when there is 1 GB or more (64 MB).
* the low memory handler now also watches semaphore usage; in the end,
we need a low resource handler, not a low memory handler.
* create_sem_etc() no longer calls vfs_free_unused_vnodes() directly as
this could actually deadlock (at least because the address space is a
R/W lock, not a recursive lock).
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resized but still had dirty pages to be written back,
vm_cache_resize() (which is called with the inode lock being held)
deadlocked with the page writer.
* Now, I reintroduced busy_writing: it'll be set by everything that
writes back pages (vm_page_write_modified(), and the page writer),
and will be checked for in vm_cache_resize() - other functions are not
affected for now, AFAICT.
* vm_cache_resize() will clear that flag, and the writer will check it
again after it wrote back the page (which will fail when it's outside
the file bounds), and if it's cleared, it will get rid of the page
(if the file has been resized again in the mean time, writing it will
succeed then, and we'll keep the page around).
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appear: when freeing a modified page, it wouldn't have a cache
anymore, but set_page_state_nolock() depended on it.
* To work around this, I added a vm_page_free() function, which the
caches that free modified pages have to call (but others may, too).
It will correctly maintain the sModifiedTemporaryPages counter in case
the cache has already been removed.
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that can be used by file systems.
* Changed the way the file cache works: instead of reading/writing to the
underlying device directly, it can now be used for any data source, ie.
also network file systems.
* As a result, the former pages_io() moved to the VFS layer, and can now be
called by a file system via {read|write}_file_io_vec_pages() (naming
suggestions are always welcomed :-)). It now gets an FD, and uses that to
communicate with the device (via its fs_{read|write}_pages() hooks).
* The file_cache_{read|write}() functions must now be called without holding
an I/O relevant file system lock. That allows the file cache to prepare the
pages without colliding with the page writer, IOW the "mayBlock" flag can
go into the attic again (yay!).
* This also results in a much better performance when the system does I/O and
is low on memory, as the page writer can now finally write back some pages,
and that even without maxing out the CPU :)
* The API changes put slightly more burden on the fs_{read|write}_pages()
hooks, but in combination with the file_map it's still pretty straight
forward. It just will have to dispatch the call to the underlying device
directly, usually it will just call its fs_{read|write}_pages() hooks
via the above mentioned calls.
* Ported BFS and FAT to the new API, the latter has not been tested, though.
* Also ported the API changes to the fs_shell. I also completely removed its
file cache level page handling - the downside is that device access is no
longer cached (ie. depends on the host OS now), the upside is that the code
is greatly simplified.
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did not propagate the "dontWait" argument, letting the page writer never wait
for its pages.
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the same pages over and over.
* Increased the priority of the page writer a bit, so that it is higher than
the one of the page daemon.
* Added a sModifiedTemporaryPages counter to let the page_writer decide how
many pages are there to write back (temporary pages would go to the swap file
and are only written back when memory is low).
* In case there are more than 1024 modified (non-temporary) pages around, the
page writer will constantly write out pages, not only when being pushed.
* The page writer now temporarily always leave out temporary pages (as long as
we don't have a swap file).
* Shuffled functions around a bit.
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on pages are recorded in a history and can be printed via the
"page_allocations" command.
* Fixed a problem in the page scrubber. It temporarily removed pages
from the free list, which could have been reserved by someone else.
When actually allocating the reserved pages, that someone could find
free and clear lists empty and would therefore rightfully panic
("Had reserved page, but there is none!").
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non-reserve case.
* vm_page_allocate_page() could also lose a stolen page in case more free pages were available
after steal_pages() was called.
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vm_page_reserve_pages() and vm_page_allocate_page() will now steal pages from
the inactive queue as needed.
* We currently never steal active pages anymore, but this might need to be
revised later (therefore, the page scanner never waits anymore, but uses
mutex_trylock() to lock a cache).
* The page scanner and writer now both run at normal priority - let's see how
that will work out.
* Introduced an inactive queue.
* Instead of shuffling pages around in the queue (and therefore destroying LRU)
the page stealing mechanism now uses a marker page to be able to release the
page lock without losing its position in the queue.
* The page writer now always grabs the whole release count of the semaphore, so
that there won't be a huge backlog to catch up with.
* vm_page_num_free_pages() now also includes the inactive queue as well as the
reserved pages (they are no longer regarded as free pages).
* Added a insert_page_after() function that inserts a page after another one,
needed by the marker code.
* clear_page() now gets a vm_page instead of a physical address which simplified
some code.
* Removed superfluous initialization of the queues (if those aren't zeroed on
start, we would have serious problems, anyway).
* Removed old and unimplemented dump_free_page_table() ("free_pages") KDL
command.
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vm_remove_all_page_mappings() all computed the wrong virtual address for the
page in question, and would therefore return incorrect data!
Introduced a virtual_page_address() function that is now used by all of them.
So that's why we were still "losing" modified flags - it took me some hours
to find those (sometimes processes died after stealing pages)...
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it intended to. That resulted in more writable pages where you wouldn't want
them (ie. allowing the area to change pages in lower caches).
* We were losing modified pages: vm_unmap_pages() sometimes has to preserve
the modified flag (eg. when called from page fault).
* Both of these were responsible that stealing active pages would crash
applications - even if less likely, this could also have happened when
stealing inactive pages. Therefore, I've activated stealing active pages
again.
* The page writer now pushes the pages of busy vnodes to the end of the queue,
so that it won't pick them up again too soon (the vnode destruction would
be in the process of writing those pages back, anyway).
* The page thief now triggers the page writer to run once it has to steal
active pages. This might be a bit too aggressive, though.
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* The page_thief() will no longer steal any pages in B_LOW_MEMORY_NOTE state,
only in the more serious cases.
* I've disabled stealing active pages for now again; there seem to be some
problems with it (either with how we do it, or with other stuff).
* vm_page_schedule_write_page() now always releases the page writer semaphore,
resulting in many more written pages - this isn't optimal as long as there is
no I/O scheduler, but before it was much too rare when there are many dirty
pages.
* Customized the thread priorities a bit to make the page scanner/thief/writer
experience a bit nicer with our current scheduler.
* vm_page_reserve_pages() would return too early, it did not test if really
enough pages are free.
* Under certain circumstances, the wakeup from vm_page_reserve_pages() did not
work - we now always notify in vm_page_unreserve_pages() to work around that
problem.
* Checked if the page reservations are done when needed and are always balanced
for the whole kernel.
* vm_page_allocate_page() now panics if it can't deliver a reserved page.
* vm_page_allocate_page_run() can no longer steal reserved pages.
* With all of those changes, I could finally copy a file in emulation, ie. the
Luposian bug should finally be fixed, even though the system might still not
be perfectly stable under low memory. Will do some more testing.
* write_page() no longer prints something on failure.
* Dumping a whole page queue will now also write the cache type of each page.
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* vm_low_memory_state() now periodically recomputes the state in case the
low memory thread is waiting for something.
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allocate with the vm_cache locked - this is necessary to be able to steal pages
from itself (large files...).
The system doesn't actually lock up anymore, but it still renders itself unusable;
obviously the page thief does not work correctly, yet. The rest of the experience
is created by our current scheduler (the page thief runs and runs, but it doesn't
free any pages anymore).
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* his has to be used by the page writer to make sure the vnode is still valid.
* This should have been the final nail on the Luposian bug - I haven't tested
it yet, but we'll certainly see :-)
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interfere with the page thief, we always need to have reserved a page for
this upfront. I introduced a function to the vm_translation_map layer that
estimates how much pages a mapping might need at maximum. All functions that
map a page now call this and reserve the needed pages upfront.
It might not be a nice solution, but it works.
* The page thief could run into a panic when trying to call vm_cache_release_ref()
on a non-existing (NULL) cache.
* Also, it will now ignore wired active pages.
* There is still a race condition between the page writer and the vnode
destruction - writing a page back needs a valid vnode, but that might just
have been deleted.
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(currently, wired pages don't always have the PAGE_STATE_WIRED, but a
wired_count).
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the unmapped page.
* This is needed by everyone who calls this to make sure modifications to a
page aren't ignored. Namely, the page scanner and the page thief were
affected.
* Cleaned up locking the page's cache a bit in page_thief(); there is now
a helper class that takes care of everything.
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* the page writer don't allow to block, while all other writers do. This fixes
bug #1509. The reason the page writer needs this is because it marks several
pages from different caches as busy.
* Fixed a warning about ASSERT being defined already in BFS, since
util/DoublyLinkedList.h now includes debug.h.
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could be written back. This should stop the page thief from stealing active
pages that cannot be recreated easily :-)
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necessary because low memory handlers might need to wait for other services
while we need to make sure the page thief can always steal pages.
* Made the page thief more aggressive when memory is critical: added a third
run where it will also steal a small amount of active pages to keep things
going.
* The page thief did not maintain the cache's reference correctly in all
situations.
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components - now, we divide the initialization of that service into two parts
which allows this (before, most handlers were gone after boot).
* Added debugger command that dumps the low memory handlers.
* The slab allocator now registers its low memory handler with a higher
priority, so that it'll run before the potentially heavier ones.
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inserted into the list according to their priority; higher priority
handlers are now called first.
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Apparently not everyone checks the page state for PAGE_STATE_BUSY.
vm_page_write_modified_pages() does now at least.
* Fixed typos in comments.
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* We now have a page writer that takes some pages from the modified queue
and writes it back every few seconds. It can be triggered by the page
scanner to do that more often, though. That mechanism can be greatly
improved once we have our I/O scheduler working.
* Removed vm_page_write_modified_page() again - it was all "eaten up" by
the page writer.
* Reworked vm_page_write_modified_pages() a bit: it now uses
vm_test_map_modification() and vm_clear_map_flags() instead of the
iterating over all areas which wouldn't even work correctly.
The code is much simpler now, too.
* You usually put something to the tail of a queue, and remove the contents
from the head, not vice versa - changed queue implementation to reflect this.
* Additionally, there is now a enqueue_page_to_head() if you actually want the
opposite.
* vm_page_requeue() allows you to move a page in a queue to the head or tail.
* Replaced vm_clear_map_activation() with vm_clear_map_flags() which allows
you to clear other flags than PAGE_ACCESSED.
* The page scanner dumps now some arguments with each run.
* Removed the old disabled pageout_daemon() from NewOS.
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to the private VM types are including vm_types.h now.
* Removed vm_page, vm_area, vm_cache, and vm_address_space typedefs; it's
cleaner this way, and the actual types are only used in C++ files now,
anyway.
* And that caused changes in many files...
* Made commpage.h self-containing.
* Minor cleanup.
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in enqueue_page() - it doesn't really belong there.
* Minor cleanup.
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For some reason, shell wildcards do not include deleted files... :)
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