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      1 /*	$NetBSD: shrinker.h,v 1.5 2021/12/19 01:22:37 riastradh Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2013 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Taylor R. Campbell.
      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 _LINUX_SHRINKER_H_
     33 #define _LINUX_SHRINKER_H_
     34 
     35 #include <uvm/uvm.h>
     36 
     37 struct shrink_control {
     38 	unsigned long	nr_to_scan;
     39 	unsigned long	nr_scanned;
     40 };
     41 
     42 struct shrinker {
     43 	int		(*shrink)(struct shrinker *, struct shrink_control *);
     44 	unsigned long	(*count_objects)(struct shrinker *,
     45 			    struct shrink_control *);
     46 	unsigned long	(*scan_objects)(struct shrinker *,
     47 			    struct shrink_control *);
     48 	int		seeks;
     49 	size_t		batch;
     50 };
     51 
     52 #define	SHRINK_STOP	(~0UL)
     53 
     54 #define	DEFAULT_SEEKS	2	/* XXX cargo-culted from Linux */
     55 
     56 static inline int
     57 register_shrinker(struct shrinker *shrinker __unused)
     58 {
     59 	return 0;
     60 }
     61 
     62 static inline void
     63 unregister_shrinker(struct shrinker *shrinker __unused)
     64 {
     65 }
     66 
     67 static inline bool
     68 current_is_kswapd(void)
     69 {
     70 	return curlwp == uvm.pagedaemon_lwp;
     71 }
     72 
     73 static inline size_t
     74 get_nr_swap_pages(void)
     75 {
     76 	return uvmexp.swpages;
     77 }
     78 
     79 #endif  /* _LINUX_SHRINKER_H_ */
     80