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      1 /*	$NetBSD: uvm_pglist.h,v 1.11 2020/04/13 15:16:14 ad Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2000, 2001, 2008, 2019 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Jason R. Thorpe, and by Andrew Doran.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     29  * POSSIBILITY OF SUCH DAMAGE.
     30  */
     31 
     32 #ifndef _UVM_UVM_PGLIST_H_
     33 #define _UVM_UVM_PGLIST_H_
     34 
     35 #include <sys/param.h>
     36 
     37 /*
     38  * This defines the type of a page queue, e.g. active list, inactive
     39  * list, etc.
     40  */
     41 struct vm_page;
     42 TAILQ_HEAD(pglist, vm_page);
     43 LIST_HEAD(pgflist, vm_page);
     44 
     45 /*
     46  * The global uvm.page_free list (uvm_page.c, uvm_pglist.c).  Free pages are
     47  * stored according to freelist, bucket, and cache colour.
     48  *
     49  * pglist = &uvm.page_free[freelist].pgfl_buckets[bucket].pgb_color[color];
     50  *
     51  * Freelists provide a priority ordering of pages for allocation, based upon
     52  * how valuable they are for special uses (e.g.  device driver DMA).  MD
     53  * code decides the number and structure of these.  They are always arranged
     54  * in descending order of allocation priority.
     55  *
     56  * Pages are then grouped in buckets according to some common factor, for
     57  * example L2/L3 cache locality.  Each bucket has its own lock, and the
     58  * locks are shared among freelists for the same numbered buckets.
     59  *
     60  * Inside each bucket, pages are further distributed by cache color.
     61  *
     62  * We want these data structures to occupy as few cache lines as possible,
     63  * as they will be highly contended.
     64  */
     65 struct pgflbucket {
     66 	uintptr_t	pgb_nfree;	/* total # free pages, all colors */
     67 	struct pgflist	pgb_colors[1];	/* variable size array */
     68 };
     69 
     70 /*
     71  * 8 buckets should be enough to cover most all current x86 systems (2019),
     72  * given the way package/core/smt IDs are structured on x86.  For systems
     73  * that report high package counts despite having a single physical CPU
     74  * package (e.g. Ampere eMAG) a little bit of sharing isn't going to hurt.
     75  */
     76 #define	PGFL_MAX_BUCKETS	8
     77 struct pgfreelist {
     78 	struct pgflbucket	*pgfl_buckets[PGFL_MAX_BUCKETS];
     79 };
     80 
     81 /*
     82  * Lock for each bucket.
     83  */
     84 union uvm_freelist_lock {
     85         kmutex_t        lock;
     86         uint8_t         padding[COHERENCY_UNIT];
     87 };
     88 extern union uvm_freelist_lock	uvm_freelist_locks[PGFL_MAX_BUCKETS];
     89 
     90 #endif /* _UVM_UVM_PGLIST_H_ */
     91