From 24f7c6b981fb70084757382da464ea85d72af300 Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Wed, 28 Aug 2013 10:17:56 +1000 Subject: mm: new shrinker API MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The current shrinker callout API uses an a single shrinker call for multiple functions. To determine the function, a special magical value is passed in a parameter to change the behaviour. This complicates the implementation and return value specification for the different behaviours. Separate the two different behaviours into separate operations, one to return a count of freeable objects in the cache, and another to scan a certain number of objects in the cache for freeing. In defining these new operations, ensure the return values and resultant behaviours are clearly defined and documented. Modify shrink_slab() to use the new API and implement the callouts for all the existing shrinkers. Signed-off-by: Dave Chinner Signed-off-by: Glauber Costa Acked-by: Mel Gorman Cc: "Theodore Ts'o" Cc: Adrian Hunter Cc: Al Viro Cc: Artem Bityutskiy Cc: Arve Hjønnevåg Cc: Carlos Maiolino Cc: Christoph Hellwig Cc: Chuck Lever Cc: Daniel Vetter Cc: David Rientjes Cc: Gleb Natapov Cc: Greg Thelen Cc: J. Bruce Fields Cc: Jan Kara Cc: Jerome Glisse Cc: John Stultz Cc: KAMEZAWA Hiroyuki Cc: Kent Overstreet Cc: Kirill A. Shutemov Cc: Marcelo Tosatti Cc: Mel Gorman Cc: Steven Whitehouse Cc: Thomas Hellstrom Cc: Trond Myklebust Signed-off-by: Andrew Morton Signed-off-by: Al Viro --- include/linux/shrinker.h | 38 +++++++++++++++++++++++++++++--------- 1 file changed, 29 insertions(+), 9 deletions(-) (limited to 'include/linux/shrinker.h') diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h index ac6b8ee07825..884e76222e1b 100644 --- a/include/linux/shrinker.h +++ b/include/linux/shrinker.h @@ -4,6 +4,12 @@ /* * This struct is used to pass information from page reclaim to the shrinkers. * We consolidate the values for easier extention later. + * + * 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. */ struct shrink_control { gfp_t gfp_mask; @@ -12,23 +18,37 @@ struct shrink_control { unsigned long nr_to_scan; }; +#define SHRINK_STOP (~0UL) /* * A callback you can register to apply pressure to ageable caches. * - * 'sc' is passed shrink_control which includes 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). + * @shrink() 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 'gfpmask' refers to the allocation we are currently trying to - * fulfil. + * @count_objects should return the number of freeable items in the cache. If + * there are no objects to free or the number of freeable items cannot be + * determined, it should return 0. No deadlock checks should be done during the + * count callback - the shrinker relies on aggregating scan counts that couldn't + * be executed due to potential deadlocks to be run at a later call when the + * deadlock condition is no longer pending. * - * 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. + * @scan_objects will only be called if @count_objects returned a non-zero + * value for the number of freeable objects. The callout should scan the cache + * and attempt to free items from the cache. It should then return the number + * of objects freed during the scan, or SHRINK_STOP if progress cannot be made + * due to potential deadlocks. If SHRINK_STOP is returned, then no further + * attempts to call the @scan_objects will be made from the current reclaim + * context. */ struct shrinker { int (*shrink)(struct shrinker *, struct shrink_control *sc); + unsigned long (*count_objects)(struct shrinker *, + struct shrink_control *sc); + unsigned long (*scan_objects)(struct shrinker *, + struct shrink_control *sc); + int seeks; /* seeks to recreate an obj */ long batch; /* reclaim batch size, 0 = default */ -- cgit v1.2.3 From 0ce3d74450815500e31f16a0b65f6bab687985c3 Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Wed, 28 Aug 2013 10:18:03 +1000 Subject: shrinker: add node awareness MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Pass the node of the current zone being reclaimed to shrink_slab(), allowing the shrinker control nodemask to be set appropriately for node aware shrinkers. Signed-off-by: Dave Chinner Signed-off-by: Glauber Costa Acked-by: Mel Gorman Cc: "Theodore Ts'o" Cc: Adrian Hunter Cc: Al Viro Cc: Artem Bityutskiy Cc: Arve Hjønnevåg Cc: Carlos Maiolino Cc: Christoph Hellwig Cc: Chuck Lever Cc: Daniel Vetter Cc: David Rientjes Cc: Gleb Natapov Cc: Greg Thelen Cc: J. Bruce Fields Cc: Jan Kara Cc: Jerome Glisse Cc: John Stultz Cc: KAMEZAWA Hiroyuki Cc: Kent Overstreet Cc: Kirill A. Shutemov Cc: Marcelo Tosatti Cc: Mel Gorman Cc: Steven Whitehouse Cc: Thomas Hellstrom Cc: Trond Myklebust Signed-off-by: Andrew Morton Signed-off-by: Al Viro --- include/linux/shrinker.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'include/linux/shrinker.h') diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h index 884e76222e1b..76f520c4c394 100644 --- a/include/linux/shrinker.h +++ b/include/linux/shrinker.h @@ -16,6 +16,9 @@ struct shrink_control { /* How many slab objects shrinker() should scan and try to reclaim */ unsigned long nr_to_scan; + + /* shrink from these nodes */ + nodemask_t nodes_to_scan; }; #define SHRINK_STOP (~0UL) -- cgit v1.2.3 From 1d3d4437eae1bb2963faab427f65f90663c64aa1 Mon Sep 17 00:00:00 2001 From: Glauber Costa Date: Wed, 28 Aug 2013 10:18:04 +1000 Subject: vmscan: per-node deferred work MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The list_lru infrastructure already keeps per-node LRU lists in its node-specific list_lru_node arrays and provide us with a per-node API, and the shrinkers are properly equiped with node information. This means that we can now focus our shrinking effort in a single node, but the work that is deferred from one run to another is kept global at nr_in_batch. Work can be deferred, for instance, during direct reclaim under a GFP_NOFS allocation, where situation, all the filesystem shrinkers will be prevented from running and accumulate in nr_in_batch the amount of work they should have done, but could not. This creates an impedance problem, where upon node pressure, work deferred will accumulate and end up being flushed in other nodes. The problem we describe is particularly harmful in big machines, where many nodes can accumulate at the same time, all adding to the global counter nr_in_batch. As we accumulate more and more, we start to ask for the caches to flush even bigger numbers. The result is that the caches are depleted and do not stabilize. To achieve stable steady state behavior, we need to tackle it differently. In this patch we keep the deferred count per-node, in the new array nr_deferred[] (the name is also a bit more descriptive) and will never accumulate that to other nodes. Signed-off-by: Glauber Costa Cc: Dave Chinner Cc: Mel Gorman Cc: "Theodore Ts'o" Cc: Adrian Hunter Cc: Al Viro Cc: Artem Bityutskiy Cc: Arve Hjønnevåg Cc: Carlos Maiolino Cc: Christoph Hellwig Cc: Chuck Lever Cc: Daniel Vetter Cc: David Rientjes Cc: Gleb Natapov Cc: Greg Thelen Cc: J. Bruce Fields Cc: Jan Kara Cc: Jerome Glisse Cc: John Stultz Cc: KAMEZAWA Hiroyuki Cc: Kent Overstreet Cc: Kirill A. Shutemov Cc: Marcelo Tosatti Cc: Mel Gorman Cc: Steven Whitehouse Cc: Thomas Hellstrom Cc: Trond Myklebust Signed-off-by: Andrew Morton Signed-off-by: Al Viro --- include/linux/shrinker.h | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) (limited to 'include/linux/shrinker.h') diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h index 76f520c4c394..8f80f243fed9 100644 --- a/include/linux/shrinker.h +++ b/include/linux/shrinker.h @@ -19,6 +19,8 @@ struct shrink_control { /* shrink from these nodes */ nodemask_t nodes_to_scan; + /* current node being shrunk (for NUMA aware shrinkers) */ + int nid; }; #define SHRINK_STOP (~0UL) @@ -44,6 +46,8 @@ struct shrink_control { * due to potential deadlocks. If SHRINK_STOP is returned, then no further * attempts to call the @scan_objects will be made from the current reclaim * context. + * + * @flags determine the shrinker abilities, like numa awareness */ struct shrinker { int (*shrink)(struct shrinker *, struct shrink_control *sc); @@ -54,12 +58,18 @@ struct shrinker { int seeks; /* seeks to recreate an obj */ long batch; /* reclaim batch size, 0 = default */ + unsigned long flags; /* These are for internal use */ struct list_head list; - atomic_long_t nr_in_batch; /* objs pending delete */ + /* objs pending delete, per node */ + atomic_long_t *nr_deferred; }; #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */ -extern void register_shrinker(struct shrinker *); + +/* Flags */ +#define SHRINKER_NUMA_AWARE (1 << 0) + +extern int register_shrinker(struct shrinker *); extern void unregister_shrinker(struct shrinker *); #endif -- cgit v1.2.3 From a0b02131c5fcd8545b867db72224b3659e813f10 Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Wed, 28 Aug 2013 10:18:16 +1000 Subject: shrinker: Kill old ->shrink API. MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit There are no more users of this API, so kill it dead, dead, dead and quietly bury the corpse in a shallow, unmarked grave in a dark forest deep in the hills... [glommer@openvz.org: added flowers to the grave] Signed-off-by: Dave Chinner Signed-off-by: Glauber Costa Reviewed-by: Greg Thelen Acked-by: Mel Gorman Cc: "Theodore Ts'o" Cc: Adrian Hunter Cc: Al Viro Cc: Artem Bityutskiy Cc: Arve Hjønnevåg Cc: Carlos Maiolino Cc: Christoph Hellwig Cc: Chuck Lever Cc: Daniel Vetter Cc: David Rientjes Cc: Gleb Natapov Cc: Greg Thelen Cc: J. Bruce Fields Cc: Jan Kara Cc: Jerome Glisse Cc: John Stultz Cc: KAMEZAWA Hiroyuki Cc: Kent Overstreet Cc: Kirill A. Shutemov Cc: Marcelo Tosatti Cc: Mel Gorman Cc: Steven Whitehouse Cc: Thomas Hellstrom Cc: Trond Myklebust Signed-off-by: Andrew Morton Signed-off-by: Al Viro --- include/linux/shrinker.h | 15 +++++---------- 1 file changed, 5 insertions(+), 10 deletions(-) (limited to 'include/linux/shrinker.h') diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h index 8f80f243fed9..68c097077ef0 100644 --- a/include/linux/shrinker.h +++ b/include/linux/shrinker.h @@ -7,14 +7,15 @@ * * 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. */ struct shrink_control { gfp_t gfp_mask; - /* How many slab objects shrinker() should scan and try to reclaim */ + /* + * How many objects scan_objects should scan and try to reclaim. + * This is reset before every call, so it is safe for callees + * to modify. + */ unsigned long nr_to_scan; /* shrink from these nodes */ @@ -27,11 +28,6 @@ struct shrink_control { /* * A callback you can register to apply pressure to ageable caches. * - * @shrink() 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). - * * @count_objects should return the number of freeable items in the cache. If * there are no objects to free or the number of freeable items cannot be * determined, it should return 0. No deadlock checks should be done during the @@ -50,7 +46,6 @@ struct shrink_control { * @flags determine the shrinker abilities, like numa awareness */ struct shrinker { - int (*shrink)(struct shrinker *, struct shrink_control *sc); unsigned long (*count_objects)(struct shrinker *, struct shrink_control *sc); unsigned long (*scan_objects)(struct shrinker *, -- cgit v1.2.3