Remove VI_OBJDIRTY and make sure that OBJ_MIGHTBEDIRTY is set only for vnode-backed vm objects.
a device pager (OBJT_DEVICE) object in that it uses fictitious pages to provide aliases to other memory addresses. The primary difference is that it uses an sglist(9) to determine the physical addresses for a given offset into the object instead of invoking the d_mmap() method in a device driver. Reviewed by: alc Approved by: re (kensmith) MFC after: 2 weeks
dependent memory attributes:
Rename vm_cache_mode_t to vm_memattr_t. The new name reflects the
fact that there are machine-dependent memory attributes that have
nothing to do with controlling the cache's behavior.
Introduce vm_object_set_memattr() for setting the default memory
attributes that will be given to an object's pages.
Introduce and use pmap_page_{get,set}_memattr() for getting and
setting a page's machine-dependent memory attributes. Add full
support for these functions on amd64 and i386 and stubs for them on
the other architectures. The function pmap_page_set_memattr() is also
responsible for any other machine-dependent aspects of changing a
page's memory attributes, such as flushing the cache or updating the
direct map. The uses include kmem_alloc_contig(), vm_page_alloc(),
and the device pager:
kmem_alloc_contig() can now be used to allocate kernel memory with
non-default memory attributes on amd64 and i386.
vm_page_alloc() and the device pager will set the memory attributes
for the real or fictitious page according to the object's default
memory attributes.
Update the various pmap functions on amd64 and i386 that map pages to
incorporate each page's memory attributes in the mapping.
Notes: (1) Inherent to this design are safety features that prevent
the specification of inconsistent memory attributes by different
mappings on amd64 and i386. In addition, the device pager provides a
warning when a device driver creates a fictitious page with memory
attributes that are inconsistent with the real page that the
fictitious page is an alias for. (2) Storing the machine-dependent
memory attributes for amd64 and i386 as a dedicated "int" in "struct
md_page" represents a compromise between space efficiency and the ease
of MFCing these changes to RELENG_7.
In collaboration with: jhb
Approved by: re (kib)
rlimit RLIMIT_SWAP that limits the amount of swap that may be reserved for the uid. The accounting information (charge) is associated with either map entry, or vm object backing the entry, assuming the object is the first one in the shadow chain and entry does not require COW. Charge is moved from entry to object on allocation of the object, e.g. during the mmap, assuming the object is allocated, or on the first page fault on the entry. It moves back to the entry on forks due to COW setup. The per-entry granularity of accounting makes the charge process fair for processes that change uid during lifetime, and decrements charge for proper uid when region is unmapped. The interface of vm_pager_allocate(9) is extended by adding struct ucred *, that is used to charge appropriate uid when allocation if performed by kernel, e.g. md(4). Several syscalls, among them is fork(2), may now return ENOMEM when global or per-uid limits are enforced. In collaboration with: pho Reviewed by: alc Approved by: re (kensmith)
memory with 4MB pages was added to pmap_object_init_pt(). This code assumes that the pages of a OBJT_DEVICE object are always physically contiguous. Unfortunately, this is not always the case. For example, jhb@ informs me that the recently introduced /dev/ksyms driver creates a OBJT_DEVICE object that violates this assumption. Thus, this revision modifies pmap_object_init_pt() to abort the mapping if the OBJT_DEVICE object's pages are not physically contiguous. This revision also changes some inconsistent if not buggy behavior. For example, the i386 version aborts if the first 4MB virtual page that would be mapped is already valid. However, it incorrectly replaces any subsequent 4MB virtual page mappings that it encounters, potentially leaking a page table page. The amd64 version has a bug of my own creation. It potentially busies the wrong page and always an insufficent number of pages if it blocks allocating a page table page. To my knowledge, there have been no reports of these bugs, hence, their persistance. I suspect that the existing restrictions that pmap_object_init_pt() placed on the OBJT_DEVICE objects that it would choose to map, for example, that the first page must be aligned on a 2 or 4MB physical boundary and that the size of the mapping must be a multiple of the large page size, were enough to avoid triggering the bug for drivers like ksyms. However, one side effect of testing the OBJT_DEVICE object's pages for physical contiguity is that a dubious difference between pmap_object_init_pt() and the standard path for mapping devices pages, i.e., vm_fault(), has been eliminated. Previously, pmap_object_init_pt() would only instantiate the first PG_FICTITOUS page being mapped because it never examined the rest. Now, however, pmap_object_init_pt() uses the new function vm_object_populate() to instantiate them all (in order to support testing their physical contiguity). These pages need to be instantiated for the mechanism that I have prototyped for automatically maintaining the consistency of the PAT settings across multiple mappings, particularly, amd64's direct mapping, to work. (Translation: This change is also being made to support jhb@'s work on the Nvidia feature requests.) Discussed with: jhb@
redundant assertion in vm_fault(). Reviewed by: kib
Directory IO without a VM object will store data in 'malloced' buffers severely limiting caching of the data. Without this change VM objects for directories are only created on an open() of the directory. TODO: Inline test if VM object already exists to avoid locking/function call overhead. Tested by: kris@ Reviewed by: jeff@ Reported by: David Filo
Recycle the vm object's "pg_color" field to represent the color of the first virtual page address at which the object is mapped instead of the color of the object's first physical page. Since an object may not be mapped, introduce a flag "OBJ_COLORED" that indicates whether "pg_color" is valid.
ways: (1) Cached pages are no longer kept in the object's resident page splay tree and memq. Instead, they are kept in a separate per-object splay tree of cached pages. However, access to this new per-object splay tree is synchronized by the _free_ page queues lock, not to be confused with the heavily contended page queues lock. Consequently, a cached page can be reclaimed by vm_page_alloc(9) without acquiring the object's lock or the page queues lock. This solves a problem independently reported by tegge@ and Isilon. Specifically, they observed the page daemon consuming a great deal of CPU time because of pages bouncing back and forth between the cache queue (PQ_CACHE) and the inactive queue (PQ_INACTIVE). The source of this problem turned out to be a deadlock avoidance strategy employed when selecting a cached page to reclaim in vm_page_select_cache(). However, the root cause was really that reclaiming a cached page required the acquisition of an object lock while the page queues lock was already held. Thus, this change addresses the problem at its root, by eliminating the need to acquire the object's lock. Moreover, keeping cached pages in the object's primary splay tree and memq was, in effect, optimizing for the uncommon case. Cached pages are reclaimed far, far more often than they are reactivated. Instead, this change makes reclamation cheaper, especially in terms of synchronization overhead, and reactivation more expensive, because reactivated pages will have to be reentered into the object's primary splay tree and memq. (2) Cached pages are now stored alongside free pages in the physical memory allocator's buddy queues, increasing the likelihood that large allocations of contiguous physical memory (i.e., superpages) will succeed. Finally, as a result of this change long-standing restrictions on when and where a cached page can be reclaimed and returned by vm_page_alloc(9) are eliminated. Specifically, calls to vm_page_alloc(9) specifying VM_ALLOC_INTERRUPT can now reclaim and return a formerly cached page. Consequently, a call to malloc(9) specifying M_NOWAIT is less likely to fail. Discussed with: many over the course of the summer, including jeff@, Justin Husted @ Isilon, peter@, tegge@ Tested by: an earlier version by kris@ Approved by: re (kensmith)