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Commit 162453bf authored by Johannes Weiner's avatar Johannes Weiner Committed by Linus Torvalds
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mm: workingset: separate shadow unpacking and refault calculation 



Per-cgroup thrash detection will need to derive a live memcg from the
eviction cookie, and doing that inside unpack_shadow() will get nasty
with the reference handling spread over two functions.

In preparation, make unpack_shadow() clearly about extracting static
data, and let workingset_refault() do all the higher-level handling.

Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Reviewed-by: default avatarVladimir Davydov <vdavydov@virtuozzo.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 689c94f0

mm/workingset.c

+28 −28
Original line number Diff line number Diff line
@@ -165,13 +165,10 @@ static void *pack_shadow(unsigned long eviction, struct zone *zone) 
	return (void *)(eviction | RADIX_TREE_EXCEPTIONAL_ENTRY);

}



static void unpack_shadow(void *shadow,

			  struct zone **zone,

			  unsigned long *distance)

static void unpack_shadow(void *shadow, struct zone **zonep,

			  unsigned long *evictionp)

{

	unsigned long entry = (unsigned long)shadow;

	unsigned long eviction;

	unsigned long refault;

	int zid, nid;



	entry >>= RADIX_TREE_EXCEPTIONAL_SHIFT;
@@ -179,29 +176,9 @@ static void unpack_shadow(void *shadow, 
	entry >>= ZONES_SHIFT;

	nid = entry & ((1UL << NODES_SHIFT) - 1);

	entry >>= NODES_SHIFT;

	eviction = entry;



	*zone = NODE_DATA(nid)->node_zones + zid;



	refault = atomic_long_read(&(*zone)->inactive_age);



	/*

	 * The unsigned subtraction here gives an accurate distance

	 * across inactive_age overflows in most cases.

	 *

	 * There is a special case: usually, shadow entries have a

	 * short lifetime and are either refaulted or reclaimed along

	 * with the inode before they get too old.  But it is not

	 * impossible for the inactive_age to lap a shadow entry in

	 * the field, which can then can result in a false small

	 * refault distance, leading to a false activation should this

	 * old entry actually refault again.  However, earlier kernels

	 * used to deactivate unconditionally with *every* reclaim

	 * invocation for the longest time, so the occasional

	 * inappropriate activation leading to pressure on the active

	 * list is not a problem.

	 */

	*distance = (refault - eviction) & EVICTION_MASK;

	*zonep = NODE_DATA(nid)->node_zones + zid;

	*evictionp = entry;

}



/**
@@ -233,9 +210,32 @@ void *workingset_eviction(struct address_space *mapping, struct page *page) 
bool workingset_refault(void *shadow)

{

	unsigned long refault_distance;

	unsigned long eviction;

	unsigned long refault;

	struct zone *zone;



	unpack_shadow(shadow, &zone, &refault_distance);

	unpack_shadow(shadow, &zone, &eviction);



	refault = atomic_long_read(&zone->inactive_age);



	/*

	 * The unsigned subtraction here gives an accurate distance

	 * across inactive_age overflows in most cases.

	 *

	 * There is a special case: usually, shadow entries have a

	 * short lifetime and are either refaulted or reclaimed along

	 * with the inode before they get too old.  But it is not

	 * impossible for the inactive_age to lap a shadow entry in

	 * the field, which can then can result in a false small

	 * refault distance, leading to a false activation should this

	 * old entry actually refault again.  However, earlier kernels

	 * used to deactivate unconditionally with *every* reclaim

	 * invocation for the longest time, so the occasional

	 * inappropriate activation leading to pressure on the active

	 * list is not a problem.

	 */

	refault_distance = (refault - eviction) & EVICTION_MASK;



	inc_zone_state(zone, WORKINGSET_REFAULT);



	if (refault_distance <= zone_page_state(zone, NR_ACTIVE_FILE)) {