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mm: workingset: separate shadow unpacking and refault calculation

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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: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Johannes Weiner 2016-03-15 14:57:10 -07:00 committed by Linus Torvalds
parent 689c94f03a
commit 162453bfbd
1 changed files with 28 additions and 28 deletions
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56
mm/workingset.c
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@ -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)) {