uvm_map(). Change uvm_map() to honnor UVM_KMF_NOWAIT. For this, change
amap_extend() to take a flags parameter instead of just boolean for
direction, and introduce AMAP_EXTEND_FORWARDS and AMAP_EXTEND_NOWAIT flags
(AMAP_EXTEND_BACKWARDS is still defined as 0x0, to keep the code easier to
read).
Add a flag parameter to uvm_mapent_alloc().
This solves a problem a pool_get(PR_NOWAIT) could trigger a pool_get(PR_WAITOK)
in uvm_mapent_alloc().
Thanks to Chuck Silvers, enami tsugutomo, Andrew Brown and Jason R Thorpe
for feedback.
delay freeing the old am_ppref so that if we bail early due to
malloc() failures, valid ppref data hasn't been freed for no reason.
Based on comments from enami.
with:
Case #1 -- adjust offset: The slot offset in the aref can be
decremented to cover the required size addition.
Case #2 -- move pages and adjust offset: The slot offset is not large
enough, but the amap contains enough inactive space *after* the mapped
pages to make up the difference, so active slots are slid to the "end"
of the amap, and the slot offset is, again, adjusted to cover the
required size addition. This optimizes for hitting case #1 again on
the next small extension.
Case #3 -- reallocate, move pages, and adjust offset: There is not
enough inactive space in the amap, so the arrays are reallocated, and
the active pages are copied again to the "end" of the amap, and the
slot offset is adjusted to cover the required size. This also
optimizes for hitting case #1 on the next backwards extension.
This provides the missing piece in the "forward extension of
vm_map_entries" logic, so the merge failure counters have been
removed.
Not many applications will make any use of this at this time (except
for jvms and perhaps gcc3), but a "top-down" memory allocator will use
it extensively.
return failure if swap is full and there are no free physical pages.
have malloc() use this flag if M_CANFAIL is passed to it.
use M_CANFAIL to allow amap_extend() to fail when memory is scarce.
this should prevent most of the remaining hangs in low-memory situations.
deal with shortages of the VM maps where the backing pages are mapped
(usually kmem_map). Try to deal with this:
* Group all information about the backend allocator for a pool in a
separate structure. The pool references this structure, rather than
the individual fields.
* Change the pool_init() API accordingly, and adjust all callers.
* Link all pools using the same backend allocator on a list.
* The backend allocator is responsible for waiting for physical memory
to become available, but will still fail if it cannot callocate KVA
space for the pages. If this happens, carefully drain all pools using
the same backend allocator, so that some KVA space can be freed.
* Change pool_reclaim() to indicate if it actually succeeded in freeing
some pages, and use that information to make draining easier and more
efficient.
* Get rid of PR_URGENT. There was only one use of it, and it could be
dealt with by the caller.
From art@openbsd.org.
- remove special treatment of pager_map mappings in pmaps. this is
required now, since I've removed the globals that expose the address range.
pager_map now uses pmap_kenter_pa() instead of pmap_enter(), so there's
no longer any need to special-case it.
- eliminate struct uvm_vnode by moving its fields into struct vnode.
- rewrite the pageout path. the pager is now responsible for handling the
high-level requests instead of only getting control after a bunch of work
has already been done on its behalf. this will allow us to UBCify LFS,
which needs tighter control over its pages than other filesystems do.
writing a page to disk no longer requires making it read-only, which
allows us to write wired pages without causing all kinds of havoc.
- use a new PG_PAGEOUT flag to indicate that a page should be freed
on behalf of the pagedaemon when it's unlocked. this flag is very similar
to PG_RELEASED, but unlike PG_RELEASED, PG_PAGEOUT can be cleared if the
pageout fails due to eg. an indirect-block buffer being locked.
this allows us to remove the "version" field from struct vm_page,
and together with shrinking "loan_count" from 32 bits to 16,
struct vm_page is now 4 bytes smaller.
- no longer use PG_RELEASED for swap-backed pages. if the page is busy
because it's being paged out, we can't release the swap slot to be
reallocated until that write is complete, but unlike with vnodes we
don't keep a count of in-progress writes so there's no good way to
know when the write is done. instead, when we need to free a busy
swap-backed page, just sleep until we can get it busy ourselves.
- implement a fast-path for extending writes which allows us to avoid
zeroing new pages. this substantially reduces cpu usage.
- encapsulate the data used by the genfs code in a struct genfs_node,
which must be the first element of the filesystem-specific vnode data
for filesystems which use genfs_{get,put}pages().
- eliminate many of the UVM pagerops, since they aren't needed anymore
now that the pager "put" operation is a higher-level operation.
- enhance the genfs code to allow NFS to use the genfs_{get,put}pages
instead of a modified copy.
- clean up struct vnode by removing all the fields that used to be used by
the vfs_cluster.c code (which we don't use anymore with UBC).
- remove kmem_object and mb_object since they were useless.
instead of allocating pages to these objects, we now just allocate
pages with no object. such pages are mapped in the kernel until they
are freed, so we can use the mapping to find the page to free it.
this allows us to remove splvm() protection in several places.
The sum of all these changes improves write throughput on my
decstation 5000/200 to within 1% of the rate of NetBSD 1.5
and reduces the elapsed time for "make release" of a NetBSD 1.5
source tree on my 128MB pc to 10% less than a 1.5 kernel took.
amap_free(): Assert that the amap is locked.
amap_share_protect(): Assert that the amap is locked.
amap_wipeout(): Assert that the amap is locked.
uvm_anfree(): Assert that the anon has a reference count of 0 and is
not locked.
uvm_anon_lockloanpg(): Assert that the anon is locked.
anon_pagein(): Assert that the anon is locked.
uvmfault_anonget(): Assert that the anon is locked.
uvm_pagealloc_strat(): Assert that the uobj or the anon is locked
And fix the problems these have uncovered:
amap_cow_now(): Lock the new anon after allocating it, and unref and
unlock it (rather than lock!) before freeing it in case
of an error condition. This should fix a problem reported
by Dan Carosone using cdrecord on an i386 MP kernel.
uvm_fault(): Case1B -- Lock the new anon afer allocating it, and unlock
it later when we unlock the old anon.
Case2 -- Lock the new anon after allocating it, and unlock
it later by passing it to uvmfault_unlockall() (we set anon
to NULL if we're not doing a promote fault).
use queue.h macros and KASSERT().
address amap offsets in pages instead of bytes.
make amap_ref() and amap_unref() take an amap, offset and length
instead of a vm_map_entry_t.
improve whitespace and comments.
<vm/pglist.h> -> <uvm/uvm_pglist.h>
<vm/vm_inherit.h> -> <uvm/uvm_inherit.h>
<vm/vm_kern.h> -> into <uvm/uvm_extern.h>
<vm/vm_object.h> -> nothing
<vm/vm_pager.h> -> into <uvm/uvm_pager.h>
also includes a bunch of <vm/vm_page.h> include removals (due to redudancy
with <vm/vm.h>), and a scattering of other similar headers.
sub-structure malloc() failed, it was quite likely that the function
would return success incorrectly. This is this direct cause of the bug
reported in PR#7897. (Thanks to chs for helping to track it down.)
define a flag UVM_PGA_USERESERVE to allow non-kernel object
allocations to use pages from the reserve.
use the new flag for allocations in pmap modules.
- break anon related functions out of uvm_amap.c and put them in their own
file (uvm_anon.c). includes break up uvm_anon_init into an amap and an
an anon init function
- ensure that only functions within the amap module access amap structure
fields (add macros to amap api as needed)
fixes problem reported by Ken Nakata <kenn@synap.ne.jp> on the mac68k
where the stack amap chunking caused entry->end to wrap around to zero,
thus corrupting the map entry list and causing kmem_map to fill.
UVM was written by chuck cranor <chuck@maria.wustl.edu>, with some
minor portions derived from the old Mach code. i provided some help
getting swap and paging working, and other bug fixes/ideas. chuck
silvers <chuq@chuq.com> also provided some other fixes.
this is the UVM kernel code portion.
this will be KNF'd shortly. :-)
