particular it wouldn't set the flag when writing something to a page, but
only move it to the modified queue. Since mapping the page would move it to
another queue, the information that the page was modified would be lost and
it would never be written to disk. Was well reproducible with a Haiku image
build and limited amount of memory.
Fixes the hopefully last remaining cause for #5374.
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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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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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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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waits for certain events on a given page, NotifyPageEvents() wakes up
waiting threads respectively.
* Used the new feature instead of condition variables for waiting on busy
pages. We save publishing and unpublishing of a condition variable whenever
a page is marked busy. There's only something to do, if there's at least
one thread waiting in the list of the respective cache. The general
assumption is that this is only rarely the case and even if it happens,
there should be only very few threads.
* Added an apparently missing notification in cache_io(). At least I didn't
see the reason for it not being there.
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are required to be physically contiguos, which should be reworked to put them
into seperate iovecs. Still this manages to combine a great deal of page
writes into larger bursts already. Reduces the amount of IO requests being
scheduled (and greatly benefits media where page wise writes are slow when
they are accessed through a non-IOScheduler path, i.e. USB mass storage until
that is properly implemented).
* Abstracted per page page writing tasks into a PageWriteWrapper class.
* Abstracted per transfer page writing tasks into PageWriteTransfer class which
formerly was the PageWriterCallback.
* Use both classes from the PageWriterRun and from
vm_page_write_modified_page_range to remove code duplication.
* Adjusted synchronous VMAnonymousCache::Write() to cope correctly with larger
iovecs and more than one iovec. It assumed that there was exactly one page per
vector previously.
* Introduced MaxPagesPerWrite() and MaxPagesPerAsyncWrite() to VMCache to allow
a cache to specify restricitions. VMAnonymousCache does restrict the max pages
to 1 for WriteAsync right now as I didn't feel like reworking that one to cope
with non single page writes just yet.
* Pulled out PageWriteTransfer methods for better readability.
* Some typo fixes.
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cannot assume that the file is that long - we need to check for the actual
file size specifically, and then clear the extraneous bytes based on that one.
* This fixes seeing old file left-overs in the space beyond the file size in
mmapped file. Thanks to Oliver who provided me with a nice test program to
reproduce this problem (this should also fix gcc's fix_includes app (although
I wonder what it does if a file actually ends on a page boundary).
* Also fixed a bug in precaching that would cause the last page of the cache
to be discarded, causing it to be re-read later on.
* Moved partial page clearing into its own function
read_pages_and_clear_partial(), even though it's currently only used once.
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fixes#4106 for good.
* Also removed a bit of dead code in that function.
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it anymore after having called vfs_asynchronous_read_pages().
* Now, Prepare() does all the preparation work, and ReadAsync() does the actual
work - this must be called without having the cache locked. This also fixes
another bug where the callback would be deleted twice in case the I/O request
failed.
* This fixes bug #3847.
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* Did claim to have reserved pages when calling vm_page_allocate_page(), but
didn't have any (copy&paste bug). We cannot use it without reserved pages,
as we need to call vm_page_allocate_page() with a cache locked.
* No longer use low_resource_state() to determine whether to precache or not,
but use the new vm_page_num_used_pages() instead.
* Also don't (try to) precache when the cache already has more than 2/3 of its
pages to safe some unnecessary work.
* The size to precache was limited to the file size incorrectly.
* When precaching failed, the cache reference was not released.
* The precaching started one page too late, causing bug #3835.
* Reenabled precaching.
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* vfs_read_pages_async() must not be called with locked cache,
since it cannot be guaranteed that the operation will be
performed asynchronously. (The ISO9660 FS for example does not
implement the new IO hooks... yet.)
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* Implemented a way to do asynchronous pre-fetching when mapping files.
* There are slight code duplications in some places that could benefit
from cleaning up, but nothing too bad.
* Implementing smarter ways to trigger prefetching and more analysis of
the situations in the kernel would be nice. Currently up to 10 MB
of every mapped file are pre-fetched without further analysis.
* The speed improvement is nice for certain operations. On our test
system (real hardware), Firefox took 9 seconds from being launched
to display a window. Now it takes 5 seconds. Both measurements
right after booting. The same system took 35 seconds from launching
Haiku in the GRUB menu to displaying the Tracker desktop background
image. Now it takes 27 seconds.
* We didn't have the chance to check out the effects of this on the
CD boot, but potentially, they could speed it up a lot.
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* The previous code would have scheduled a single page to be written out (if it
would have ever been triggered), now we schedule the complete previous write
access. This greatly speeds up a "dd if=/dev/zero of=test ..." beyond the
size of available memory.
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IORequest.{h,cpp}.
* Introduced public <io_requests.h> header. Currently it only declares the
single function BFS uses.
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added vm_memcpy_from_physical() and vm_memcpy_physical_page(), and
added respective functions to the vm_translation_map operations. The
architecture specific implementation can now decide how to implement
them most efficiently. Added generic implementations that can be used,
though.
* Changed vm_{get,put}_physical_page(). The former no longer accepts
flags (the only flag PHYSICAL_PAGE_DONT_WAIT wasn't needed anymore).
Instead it returns an implementation-specific handle that has to be
passed to the latter. Added vm_{get,put}_physical_page_current_cpu()
and *_debug() variants, that work only for the current CPU,
respectively when in the kernel debugger. Also adjusted the
vm_translation_map operations accordingly.
* Made consequent use of the physical memory operations in the source
tree.
* Also adjusted the m68k and ppc implementations with respect to the
vm_translation_map operation changes, but they are probably broken,
nevertheless.
* For x86 the generic physical page mapper isn't used anymore. It is
suboptimal in any case. For systems with small memory it is too much
overhead, since one can just map the complete physical memory (that's
not done yet, though). For systems with large memory it counteracts
the VM strategy to reuse the least recently used pages. Since those
pages will most likely not be mapped by the page mapper anymore, it
will keep remapping chunks. This was also the reason why building
Haiku in Haiku was significantly faster with only 256 MB RAM (since
that much could be kept mapped all the time).
Now we're using a different strategy: We have small pools of virtual
page slots per CPU that are used for the physical page operations
(memset_physical(), memcpy_*_physical()) with CPU-pinned thread.
Furthermore we have four slots per translation map, which are used to
map page tables.
These changes speed up the Haiku image build in Haiku significantly. On
my Core2 Duo 2.2 GHz 2 GB machine about 40% to 20 min 40 s (KDEBUG
disabled, block cache debug disabled). Still more than factor 3 slower
than FreeBSD and Linux, though.
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{memset,memcpy_to}_physical() functions.
Mapping lots of physical pages at once as done before was an actual
problem on systems with enough RAM, as the physical page mapper can map
only 64 chunks at a time. So multiple threads could play dining
philosophers, each getting only one of two chopsticks, waiting for
another one to be freed.
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PHYSICAL_PAGE_{NO,CAN}_WAIT into an actual flag
PHYSICAL_PAGE_DONT_WAIT.
* Pass the flags through to the chunk mapper callback.
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* Added file_map_set_mode() function that you can use to keep a whole file
cached. This is needed for the swap file support: FILE_MAP_CACHE_ALL will
not only precache all file_io_vecs when called, but it will also cause all
file_map_translate() calls to fail that would require further caching (ie.
if the file size had changed).
* Updated the fs_shell file map code to the latest one (with several bug fixes).
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actual caching in the file cache, i.e. all reads and writes go directly
to the underlying device. The implementation is not quite complete,
since the VM can still add pages to the cache when the file is mmap()ed,
which can lead to inconsistencies.
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user_{memcpy,memset}(), since that can cause a page fault, which needs
pages and might try to steal some from our cache.
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partially (e.g. due to hitting the end of file). The respective
classes have grown new methods and attributes to deal with that. The
"finished" callbacks have got additional parameters to indicate
whether the transfer was only partial and how much has been
transferred. Other callbacks and functions have a size_t* in/out
parameter instead of a simple size_t, now.
* vfs_{read,write}_pages() do now use the I/O request framework instead
of the underlying FS's {read,write}_pages() hooks (those should be
unused now). Furthermore they've got an additional "flags" parameter,
which is passed to IORequest::Init(), i.e. it allows to specify that
the given vecs refer to physical addresses.
* The file cache's read_into_cache() reads directly into physical
pages, now.
* Fixed bug in DoIO::IO(): The offset was not adjusted, so that all
pages were incorrectly transferred from/to the same location.
* Fixed broken subrequest scheduling loop head in
do_iterative_fd_io_iterate().
* Adjusted the test driver and implemented its io() hook. Using this
driver I/O requests are passed all the way from the VFS/VM to the
driver and through the I/O scheduler. It even seems to work. :-)
* Added missing const to the iovec* parameter of the IORequest::Init()
methods.
* Disabled some debug output by default. Added new optional debug
output.
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fs_vnode_ops::write_pages() to be called with fsReenter = true. Since
this is no longer the case, the argument has become superfluous. For
read_pages() it always was. Removed the argument from the functions
and all functions that propagated it.
* Some whitespace at the end of lines was removed.
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introduces the following relevant changes:
* VMCache:
- Renamed vm_cache to VMCache, merged it with vm_store and made it a
C++ class with virtual methods (replacing the store operations).
Turned the different store implementations into subclasses.
- Introduced MergeStore() callback, changed semantics of Commit().
- Changed locking and referencing semantics. A reference can only be
acquired/released with the cache locked. An unreferenced cache is
deleted and a mergeable cache merged when it is unlocked. This
removes the "busy" state of a cache and simplifies the page fault
code.
* Added VMAnonymousCache, which will implement swap support (work by
Zhao Shuai). It is not integrated and used yet, though.
* Enabled the mutex/recursive lock holder asserts.
* Fixed DoublyLinkedList::Swap().
* Generalized the low memory handler to a low resource handler. And made
semaphores and reserved memory handled resources. Made
vm_try_resource_memory() optionally wait (with timeout), and used that
feature to reserve memory for areas.
...
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using it.
* IOW cache_prefetch_vnode() should work again now.
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per cache.
* Changed the strategy vm_cache_acquire_page_cache_ref() uses to ensure
that the cache isn't deleted while trying to get a reference. Instead
of the global cache pages hash table lock, it holds the global cache
list lock now. We acquire + release this lock in delete_cache() after
removing all pages and just before deleting the object.
* Some small optimizations using the property that the cache's pages are
ordered, now (vm_cache_resize(), vm_page_write_modified_page_range(),
vm_page_schedule_write_page_range()).
* Replaced some code counting a cache's pages by simply using
vm_cache::page_count.
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* Trivial adjustments of code using mutexes. Mostly removing the
mutex_init() return value check.
* Added mutex_lock_threads_locked(), which is called with the threads
spinlock being held. The spinlock is released while waiting, of
course. This function is useful in cases where the existence of the
mutex object is ensured by holding the threads spinlock.
* Changed the two instances in the VFS code where an IO context of
another team needs to be locked to use mutex_lock_threads_locked().
Before it required a semaphore-based mutex implementation.
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respective Private* base class.
* Changed sigwait() and sigsuspend() to use thread_block() instead of a
condition variable.
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file system to not fill newly created space with zeros.
BFile::SetSize() now uses this, while [f]truncate() does not. This
is only a temporary work-around until BFS supports sparse files.
* Apps that want to reserve space to fill up later should use
BFile::SetSize() for now, as this will be a lot faster than
[f]truncate().
* cache_io() and the functions below now use a special mode when you
pass in a NULL buffer: for read access, the cache is only populated
(useful for prefetching), for write access, the file is filled with
zeros.
* Implemented BFS's Inode::FillGapWithZeros() using this method now.
* Removed extraneous white space.
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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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and write_to_cache() before, IOW the cache could reserve too few pages.
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needed pages correctly, and would also not read/write enough in case the
offset didn't start at 0 resulting in undetected short reads/writes. It's
amazing how many bugs can be hidden in a few lines of code.
* Fixed a bug that might have been the cause for bug #1601: when the last part
of the write did not end on a page boundary, the last page had to be read
first, but that was done from the wrong offset. Also, if only parts of that
page could be read (because the file size didn't span over the whole page)
the remaining parts needed to be cleared.
* The cache_funcs were always called with the same value for numBytes and
bufferSize so I've eliminated the former.
* Large reads now also bypass the cache in case of low memory, large writes now
also only bypass the cache in that case, following Ingo's suggestion.
* Fixed compilation with debugging turned on.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@22858 a95241bf-73f2-0310-859d-f6bbb57e9c96
than 64KB. Reads should probably get a similar logic, at least if memory is
tight.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@22857 a95241bf-73f2-0310-859d-f6bbb57e9c96
sequential access.
* This is now used to let the cache free some pages (or schedule them to be
written back) before vm_reserve_pages() is called, but only if that cache
is not mapped, and there is a memory shortage.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@22731 a95241bf-73f2-0310-859d-f6bbb57e9c96
pages to reserve, which could result in to few being reserved in certain
situations.
* Use MutexLocker where appropriate.
* Reordered includes following the new rules.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@22494 a95241bf-73f2-0310-859d-f6bbb57e9c96
Ingo Weinhold