This makes appending the pages to the active queue more efficient and we
don't need the vm_page::is_cleared bit anymore.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@35011 a95241bf-73f2-0310-859d-f6bbb57e9c96
* Added Debug{First,Next}() methods to allow easy iteration through the
address spaces in kernel debugger commands.
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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%.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@34934 a95241bf-73f2-0310-859d-f6bbb57e9c96
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.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@34933 a95241bf-73f2-0310-859d-f6bbb57e9c96
* Renamed page_queue to VMPageQueue and made it a proper C++ class. Use
DoublyLinkedList instead of own list code.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@34874 a95241bf-73f2-0310-859d-f6bbb57e9c96
* Added VMCache::MovePage() and MoveAllPages() to move pages between caches.
* VMAnonymousCache:
- _MergeSwapPages(): Avoid doing anything, if neither cache has swapped out
pages.
- _MergeSwapPages() does now also remove source cache pages that are
shadowed by consumer swap pages. This allows us to call _MergeSwapPages()
before _MergePagesSmallerSource(), save the swap page shadowing check
there and get rid of the vm_page::merge_swap flag. This is an
optimization based on the assumption that usually none or only few pages
are swapped out, so we save a lot of checks.
- Implemented _MergePagesSmallerConsumer() as an alternative to
_MergePagesSmallerSource(). The former is used when the source cache has
more pages than the consumer cache. It iterates over the consumer cache's
pages, moves them to the source and finally moves all pages back to the
consumer. The final move is relatively cheap (though unfortunately we
still have to update all pages' vm_page::cache field), so that overall we
save iterations of the main loop with the more expensive checks.
The optimizations particularly improve the common fork()+exec*() situations.
fork() uses CoW, which is implemented by putting two new empty caches between
the to be copied area and its cache. exec*() destroys one copy of the area,
its cache and thus causes merging of the other new cache with the old cache.
Since this usually happens in a very short time, the old cache does still
contain many pages and the new cache only few. Previously the many pages were
all checked and moved individually. Now we do that for the few pages instead.
A very extreme example of this situation is the Haiku image build. jam has a
huge heap (> 200 MB) and it fork()s+exec*()s for every action to be executed.
Since during the cache merging the cache is locked, any write access to a
heap page causes jam to block until the cache merging is done. Formerly that
took so long that it killed a lot of parallelism in multi-job builds. That
could be observed particularly well when lots of small actions where executed
(like the Link, XRes, Mimeset, SetType, SetVersion combos when building
executables/libraries/add-ons). Those look dramatically better now.
The overall speed improvement for a -j8 image build on my machine is only
about 15%, though.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@34784 a95241bf-73f2-0310-859d-f6bbb57e9c96
another. The code originates from vm_copy_on_write_area(). We now generate
the VM cache tracing entries, though.
* count_writable_areas() -> VMCache::CountWritableAreas()
* Added debugger command "cache_stack" which is enabled when VM cache tracing
is enabled. It prints the source caches of a given cache or area at the
time of a specified tracing entry.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@34751 a95241bf-73f2-0310-859d-f6bbb57e9c96
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.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@34537 a95241bf-73f2-0310-859d-f6bbb57e9c96
to clarify that they never enlarge the area.
* Reimplemented VMKernelAddressSpace. It is somewhat inspired by Bonwick's
vmem resource allocator (though we have different requirements):
- We consider the complete address space to be divided into contiguous
ranges of type free, reserved, or area, each range being represented by
a VMKernelAddressRange object.
- The range objects are managed in an AVL tree and a doubly linked list
(the latter only for faster iteration) sorted by address. This provides
O(log(n)) lookup, insertion and removal.
- For each power of two size we maintain a list of free ranges of at least
that size. Thus for the most common case of B_ANY*_ADDRESS area
allocation, we find a free range in constant time (the rest of the
processing being O(log(n))) with a rather good fit. This should also
help avoiding address space fragmentation.
While the new implementation should be faster, particularly with an
increasing number of areas, I couldn't measure any difference in the -j2
haiku build. From a cursory test the -j8 build hasn't tangibly benefitted
either.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@34528 a95241bf-73f2-0310-859d-f6bbb57e9c96
link to them.
* VM{Kernel,User}AddressSpace manage the respective VMArea subclass now, and
VMAddressSpace has grown factory methods {Create,Delete}Area.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@34493 a95241bf-73f2-0310-859d-f6bbb57e9c96
new derived classes VM{Kernel,User}AddressSpace. Currently those are
identical, but that will change.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@34492 a95241bf-73f2-0310-859d-f6bbb57e9c96
pure address space feature, so it should be handled there.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@34491 a95241bf-73f2-0310-859d-f6bbb57e9c96
and size.
* Made VMArea::Set{Base,Size}() private and made VMAddressSpace a friend.
In vm.cpp the new VMAddressSpace::ResizeArea{Head,Tail}() are used
instead.
Finally all address space changes happen in VMAddressSpace only. *phew*
Now it's ready to be thoroughly butchered. :-)
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@34467 a95241bf-73f2-0310-859d-f6bbb57e9c96
This makes it more explicit where the fields are modified.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@34464 a95241bf-73f2-0310-859d-f6bbb57e9c96
simplify migration of the area management, but as a side effect, it also
makes area deletion O(1) (instead of O(n), n == number of areas in the
address space).
* Moved more area management functionality from vm.cpp to VMAddressSpace and
VMArea structure creation to VMArea. Made the list and list link members
itself private.
* VMAddressSpace tracks its amount of free space, now. This also replaces
the previous mechanism to do that only for the kernel address space. It
was broken anyway, since delete_area() subtracted the area size instead of
adding it.
* vm_free_unused_boot_loader_range():
- lastEnd could be set to a value < start, which could cause memory
outside of the given range to be unmapped. Haven't checked whether this
could happen in practice -- if so, it would be seriously unhealthy.
- The range between the end of the last area in the range and the end of
the range would never be freed.
- Fixed potential integer overflows when computing addresses.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@34459 a95241bf-73f2-0310-859d-f6bbb57e9c96
