Messages in this thread Patch in this message | | | From | Wei Yang <> | Subject | [RFC Patch] mm/vmscan.c: not inherit classzone_idx from previous reclaim | Date | Sun, 9 Feb 2020 15:41:45 +0800 |
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Before commit e716f2eb24de ("mm, vmscan: prevent kswapd sleeping prematurely due to mismatched classzone_idx"), classzone_idx could have two possibilities on a new loop based on whether there is a wakeup during reclaiming:
* 0 if no wakeup * the classzone_idx request by wakeup
As described in the changelog, this commit is willing to change the first case to (MAX_NR_ZONES - 1) to avoid some premature sleep. But it does not achieve the goal.
There are two versions of kswapd_classzone_idx() since this change:
* commit e716f2eb24de ("mm, vmscan: prevent kswapd sleeping prematurely due to mismatched classzone_idx") * commit dffcac2cb88e ("mm/vmscan.c: prevent useless kswapd loops")
Both of them would return the classzone_idx we passed as the 2nd parameter when (pgdat->kswapd_classzone_idx == MAX_NR_ZONES). This means if there is no wakeup during reclaiming, we would use classzone_idx in previous round to sleep.
This patch fixes the logic by using (MAX_NR_ZONES - 1) for the first case.
Signed-off-by: Wei Yang <richardw.yang@linux.intel.com> --- mm/vmscan.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c index e7b647f70407..ea2f0abef1d4 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -3879,7 +3879,7 @@ static void kswapd_try_to_sleep(pg_data_t *pgdat, int alloc_order, int reclaim_o static int kswapd(void *p) { unsigned int alloc_order, reclaim_order; - unsigned int classzone_idx = MAX_NR_ZONES - 1; + unsigned int classzone_idx; pg_data_t *pgdat = (pg_data_t*)p; struct task_struct *tsk = current; const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id); @@ -3908,7 +3908,7 @@ static int kswapd(void *p) bool ret; alloc_order = reclaim_order = pgdat->kswapd_order; - classzone_idx = kswapd_classzone_idx(pgdat, classzone_idx); + classzone_idx = kswapd_classzone_idx(pgdat, MAX_NR_ZONES - 1); kswapd_try_sleep: kswapd_try_to_sleep(pgdat, alloc_order, reclaim_order, -- 2.17.1
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