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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)
182 lines
5.5 KiB
C
182 lines
5.5 KiB
C
/*-
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* Copyright (c) 1990 The Regents of the University of California.
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* All rights reserved.
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* Copyright (c) 1994 John S. Dyson
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* All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* William Jolitz.
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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, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, 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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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER 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
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* SUCH DAMAGE.
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*
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* from: @(#)vmparam.h 5.9 (Berkeley) 5/12/91
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* $FreeBSD$
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*/
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#ifndef _MACHINE_VMPARAM_H_
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#define _MACHINE_VMPARAM_H_ 1
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/*
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* Machine dependent constants for 386.
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*/
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#ifndef PAE
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#define VM_PROT_READ_IS_EXEC /* if you can read -- then you can exec */
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#endif
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/*
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* Virtual memory related constants, all in bytes
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*/
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#define MAXTSIZ (128UL*1024*1024) /* max text size */
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#ifndef DFLDSIZ
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#define DFLDSIZ (128UL*1024*1024) /* initial data size limit */
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#endif
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#ifndef MAXDSIZ
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#define MAXDSIZ (512UL*1024*1024) /* max data size */
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#endif
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#ifndef DFLSSIZ
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#define DFLSSIZ (8UL*1024*1024) /* initial stack size limit */
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#endif
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#ifndef MAXSSIZ
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#define MAXSSIZ (64UL*1024*1024) /* max stack size */
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#endif
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#ifndef SGROWSIZ
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#define SGROWSIZ (128UL*1024) /* amount to grow stack */
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#endif
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/*
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* The time for a process to be blocked before being very swappable.
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* This is a number of seconds which the system takes as being a non-trivial
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* amount of real time. You probably shouldn't change this;
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* it is used in subtle ways (fractions and multiples of it are, that is, like
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* half of a ``long time'', almost a long time, etc.)
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* It is related to human patience and other factors which don't really
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* change over time.
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*/
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#define MAXSLP 20
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/*
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* The physical address space is densely populated.
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*/
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#define VM_PHYSSEG_DENSE
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/*
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* The number of PHYSSEG entries must be one greater than the number
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* of phys_avail entries because the phys_avail entry that spans the
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* largest physical address that is accessible by ISA DMA is split
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* into two PHYSSEG entries.
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*/
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#define VM_PHYSSEG_MAX 17
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/*
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* Create two free page pools. Since the i386 kernel virtual address
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* space does not include a mapping onto the machine's entire physical
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* memory, VM_FREEPOOL_DIRECT is defined as an alias for the default
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* pool, VM_FREEPOOL_DEFAULT.
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*/
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#define VM_NFREEPOOL 2
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#define VM_FREEPOOL_CACHE 1
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#define VM_FREEPOOL_DEFAULT 0
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#define VM_FREEPOOL_DIRECT 0
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/*
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* Create two free page lists: VM_FREELIST_DEFAULT is for physical
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* pages that are above the largest physical address that is
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* accessible by ISA DMA and VM_FREELIST_ISADMA is for physical pages
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* that are below that address.
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*/
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#define VM_NFREELIST 2
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#define VM_FREELIST_DEFAULT 0
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#define VM_FREELIST_ISADMA 1
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/*
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* The largest allocation size is 2MB under PAE and 4MB otherwise.
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*/
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#ifdef PAE
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#define VM_NFREEORDER 10
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#else
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#define VM_NFREEORDER 11
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#endif
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/*
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* Kernel physical load address.
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*/
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#ifndef KERNLOAD
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#define KERNLOAD (1 << PDRSHIFT)
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#endif
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/*
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* Virtual addresses of things. Derived from the page directory and
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* page table indexes from pmap.h for precision.
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* Because of the page that is both a PD and PT, it looks a little
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* messy at times, but hey, we'll do anything to save a page :-)
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*/
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#define VM_MAX_KERNEL_ADDRESS VADDR(KPTDI+NKPDE-1, NPTEPG-1)
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#define VM_MIN_KERNEL_ADDRESS VADDR(PTDPTDI, PTDPTDI)
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#define KERNBASE VADDR(KPTDI, 0)
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#define UPT_MAX_ADDRESS VADDR(PTDPTDI, PTDPTDI)
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#define UPT_MIN_ADDRESS VADDR(PTDPTDI, 0)
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#define VM_MAXUSER_ADDRESS VADDR(PTDPTDI, 0)
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#define USRSTACK VM_MAXUSER_ADDRESS
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#define VM_MAX_ADDRESS VADDR(PTDPTDI, PTDPTDI)
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#define VM_MIN_ADDRESS ((vm_offset_t)0)
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/* virtual sizes (bytes) for various kernel submaps */
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#ifndef VM_KMEM_SIZE
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#define VM_KMEM_SIZE (12 * 1024 * 1024)
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#endif
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/*
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* How many physical pages per KVA page allocated.
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* min(max(max(VM_KMEM_SIZE, Physical memory/VM_KMEM_SIZE_SCALE),
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* VM_KMEM_SIZE_MIN), VM_KMEM_SIZE_MAX)
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* is the total KVA space allocated for kmem_map.
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*/
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#ifndef VM_KMEM_SIZE_SCALE
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#define VM_KMEM_SIZE_SCALE (3)
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#endif
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/*
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* Ceiling on amount of kmem_map kva space.
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*/
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#ifndef VM_KMEM_SIZE_MAX
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#define VM_KMEM_SIZE_MAX (320 * 1024 * 1024)
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#endif
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/* initial pagein size of beginning of executable file */
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#ifndef VM_INITIAL_PAGEIN
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#define VM_INITIAL_PAGEIN 16
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#endif
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#endif /* _MACHINE_VMPARAM_H_ */
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