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mm: clean up and kernelify shrinker registration

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I can never remember what the function to register to receive VM pressure
is called.  I have to trace down from __alloc_pages() to find it.

It's called "set_shrinker()", and it needs Your Help.

1) Don't hide struct shrinker.  It contains no magic.
2) Don't allocate "struct shrinker".  It's not helpful.
3) Call them "register_shrinker" and "unregister_shrinker".
4) Call the function "shrink" not "shrinker".
5) Reduce the 17 lines of waffly comments to 13, but document it properly.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: David Chinner <dgc@sgi.com>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Rusty Russell
2007-07-17 04:03:17 -07:00
committed by Linus Torvalds
parent 5ad333eb66
commit 8e1f936b73
10 changed files with 81 additions and 74 deletions
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38
include/linux/mm.h
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@@ -810,27 +810,31 @@ extern unsigned long do_mremap(unsigned long addr,
unsigned long flags, unsigned long new_addr);
/*
* Prototype to add a shrinker callback for ageable caches.
*
* These functions are passed a count `nr_to_scan' and a gfpmask. They should
* scan `nr_to_scan' objects, attempting to free them.
* A callback you can register to apply pressure to ageable caches.
*
* The callback must return the number of objects which remain in the cache.
* 'shrink' is passed a count 'nr_to_scan' and a 'gfpmask'. It should
* look through the least-recently-used 'nr_to_scan' entries and
* attempt to free them up. It should return the number of objects
* which remain in the cache. If it returns -1, it means it cannot do
* any scanning at this time (eg. there is a risk of deadlock).
*
* The callback will be passed nr_to_scan == 0 when the VM is querying the
* cache size, so a fastpath for that case is appropriate.
* The 'gfpmask' refers to the allocation we are currently trying to
* fulfil.
*
* Note that 'shrink' will be passed nr_to_scan == 0 when the VM is
* querying the cache size, so a fastpath for that case is appropriate.
*/
typedef int (*shrinker_t)(int nr_to_scan, gfp_t gfp_mask);
struct shrinker {
int (*shrink)(int nr_to_scan, gfp_t gfp_mask);
int seeks; /* seeks to recreate an obj */
/*
* Add an aging callback. The int is the number of 'seeks' it takes
* to recreate one of the objects that these functions age.
*/
#define DEFAULT_SEEKS 2
struct shrinker;
extern struct shrinker *set_shrinker(int, shrinker_t);
extern void remove_shrinker(struct shrinker *shrinker);
/* These are for internal use */
struct list_head list;
long nr; /* objs pending delete */
};
#define DEFAULT_SEEKS 2 /* A good number if you don't know better. */
extern void register_shrinker(struct shrinker *);
extern void unregister_shrinker(struct shrinker *);
/*
* Some shared mappigns will want the pages marked read-only