On Thu, Apr 04, 2019 at 11:30:17AM +0800, Zhaoyang Huang wrote: > +++ b/mm/workingset.c > @@ -159,7 +159,7 @@ > NODES_SHIFT + \ > MEM_CGROUP_ID_SHIFT) > #define EVICTION_MASK (~0UL >> EVICTION_SHIFT) > - > +#define EVICTION_JIFFIES (BITS_PER_LONG >> 3) > /* > * Eviction timestamps need to be able to cover the full range of > * actionable refaults. However, bits are tight in the radix tree > @@ -175,18 +175,22 @@ static void *pack_shadow(int memcgid, pg_data_t *pgdat, unsigned long eviction) > eviction >>= bucket_order; > eviction = (eviction << MEM_CGROUP_ID_SHIFT) | memcgid; > eviction = (eviction << NODES_SHIFT) | pgdat->node_id; > + eviction = (eviction << EVICTION_JIFFIES) | (jiffies >> EVICTION_JIFFIES); > eviction = (eviction << RADIX_TREE_EXCEPTIONAL_SHIFT); ... this isn't against current, or even 5.0. > entry >>= RADIX_TREE_EXCEPTIONAL_SHIFT; > + entry >>= EVICTION_JIFFIES; > + prev_jiff = (entry & ((1UL << EVICTION_JIFFIES) - 1)) << EVICTION_JIFFIES; These two lines are in the wrong order. So you're getting (effectively) a random answer in your 'prev_jiff', which means your testing isn't thorough enough. I suspect you're only testing cases you're expecting to improve, and you aren't testing to make sure that other cases don't regress.
