c7aebda8a1
Unify the 2 concept into a real, minimal, sxlock where the shared acquisition represent the soft busy and the exclusive acquisition represent the hard busy. The old VPO_WANTED mechanism becames the hard-path for this new lock and it becomes per-page rather than per-object. The vm_object lock becames an interlock for this functionality: it can be held in both read or write mode. However, if the vm_object lock is held in read mode while acquiring or releasing the busy state, the thread owner cannot make any assumption on the busy state unless it is also busying it. Also: - Add a new flag to directly shared busy pages while vm_page_alloc and vm_page_grab are being executed. This will be very helpful once these functions happen under a read object lock. - Move the swapping sleep into its own per-object flag The KPI is heavilly changed this is why the version is bumped. It is very likely that some VM ports users will need to change their own code. Sponsored by: EMC / Isilon storage division Discussed with: alc Reviewed by: jeff, kib Tested by: gavin, bapt (older version) Tested by: pho, scottl
140 lines
4.3 KiB
Groff
140 lines
4.3 KiB
Groff
.\"
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.\" Copyright (C) 2001 Chad David <davidc@acns.ab.ca>. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice(s), this list of conditions and the following disclaimer as
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.\" the first lines of this file unmodified other than the possible
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.\" addition of one or more copyright notices.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice(s), this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
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.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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.\" DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
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.\" DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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.\" (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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.\" SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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.\" CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
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.\" DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd January 28, 2012
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.Dt VM_PAGE_ALLOC 9
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.Os
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.Sh NAME
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.Nm vm_page_alloc
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.Nd "allocate a page for a"
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.Vt vm_object
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.Sh SYNOPSIS
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.In sys/param.h
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.In vm/vm.h
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.In vm/vm_page.h
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.Ft vm_page_t
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.Fn vm_page_alloc "vm_object_t object" "vm_pindex_t pindex" "int req"
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.Sh DESCRIPTION
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The
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.Fn vm_page_alloc
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function allocates a page at
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.Fa pindex
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within
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.Fa object .
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It is assumed that a page has not already been allocated at
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.Fa pindex .
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The page returned is inserted into the object, unless
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.Dv VM_ALLOC_NOOBJ
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is specified in the
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.Fa req .
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The page may exist in the vm object cache, in which case it will
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be reactivated instead, moving from the cache into the object page list.
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.Pp
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.Fn vm_page_alloc
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will not sleep.
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.Pp
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Its arguments are:
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.Bl -tag -width ".Fa object"
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.It Fa object
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The VM object to allocate the page for.
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The
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.Fa object
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must be locked if
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.Dv VM_ALLOC_NOOBJ
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is not specified.
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.It Fa pindex
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The index into the object at which the page should be inserted.
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.It Fa req
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The bitwise-inclusive OR of a class and any optional flags indicating
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how the page should be allocated.
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.Pp
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Exactly one of the following classes must be specified:
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.Bl -tag -width ".Dv VM_ALLOC_INTERRUPT"
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.It Dv VM_ALLOC_NORMAL
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The page should be allocated with no special treatment.
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.It Dv VM_ALLOC_SYSTEM
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The page can be allocated if the cache is empty and the free
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page count is above the interrupt reserved water mark.
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This flag should be used only when the system really needs the page.
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.It Dv VM_ALLOC_INTERRUPT
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.Fn vm_page_alloc
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is being called during an interrupt.
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A page will be returned successfully if the free page count is greater
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than zero.
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.El
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.Pp
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The optional flags are:
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.Bl -tag -width ".Dv VM_ALLOC_IFNOTCACHED"
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.It Dv VM_ALLOC_NOBUSY
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The returned page will not be exclusive busy.
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.It Dv VM_ALLOC_NODUMP
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The returned page will not be included in any kernel core dumps
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regardless of whether or not it is mapped in to KVA.
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.It Dv VM_ALLOC_NOOBJ
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Do not associate the allocated page with a vm object.
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The
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.Fa object
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argument is ignored.
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.It Dv VM_ALLOC_IFCACHED
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Allocate the page only if it is cached.
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Otherwise, return
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.Dv NULL .
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.It Dv VM_ALLOC_IFNOTCACHED
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Only allocate the page if it is not cached in the
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.Fa object .
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If the page at the specified
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.Fa pindex
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is cached, NULL is returned instead.
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.It Dv VM_ALLOC_SBUSY
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The returned page will be shared busy.
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.It Dv VM_ALLOC_WIRED
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The returned page will be wired.
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.It Dv VM_ALLOC_ZERO
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Indicate a preference for a pre-zeroed page.
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There is no guarantee that the returned page will be zeroed, but it
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will have the
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.Dv PG_ZERO
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flag set if it is zeroed.
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.El
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.El
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.Sh RETURN VALUES
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The
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.Vt vm_page_t
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that was allocated is returned if successful; otherwise,
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.Dv NULL
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is returned.
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.Sh NOTES
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The pager process is always upgraded to
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.Dv VM_ALLOC_SYSTEM
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unless
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.Dv VM_ALLOC_INTERRUPT
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is set.
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.Sh AUTHORS
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This manual page was written by
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.An Chad David Aq davidc@acns.ab.ca .
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