On Mon, 5 Oct 2009, Lee Schermerhorn wrote:
> [PATCH 11/11] hugetlb: offload [un]registration of sysfs attr to worker thread
>
> Against: 2.6.31-mmotm-090925-1435
>
> New in V6
>
> V7: + remove redundant check for memory{ful|less} node from
> node_hugetlb_work(). Rely on [added] return from
> hugetlb_register_node() to differentiate between transitions
> to/from memoryless state.
>
That doesn't work because the memory hotplug code doesn't clear the
N_HIGH_MEMORY bit for status_change_nid on MEM_OFFLINE, so
hugetlb_register_node() will always return true under such conditions.
The following should fix it. Christoph?
mm: clear node in N_HIGH_MEMORY and stop kswapd when all memory is offlined
When memory is hot-removed, its node must be cleared in N_HIGH_MEMORY if
there are no present pages left.
In such a situation, kswapd must also be stopped since it has nothing
left to do.
Cc: Christoph Lameter <cl@xxxxxxxxxxxxxxxxxxxx>
Cc: Yasunori Goto <y-goto@xxxxxxxxxxxxxx>
Cc: Mel Gorman <mel@xxxxxxxxx>
Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
---
include/linux/swap.h | 1 +
mm/memory_hotplug.c | 4 ++++
mm/vmscan.c | 28 ++++++++++++++++++++++------
3 files changed, 27 insertions(+), 6 deletions(-)
diff --git a/include/linux/swap.h b/include/linux/swap.h
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -273,6 +273,7 @@ extern int scan_unevictable_register_node(struct node *node);
extern void scan_unevictable_unregister_node(struct node *node);
extern int kswapd_run(int nid);
+extern void kswapd_stop(int nid);
#ifdef CONFIG_MMU
/* linux/mm/shmem.c */
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -838,6 +838,10 @@ repeat:
setup_per_zone_wmarks();
calculate_zone_inactive_ratio(zone);
+ if (!node_present_pages(node)) {
+ node_clear_state(node, N_HIGH_MEMORY);
+ kswapd_stop(node);
+ }
vm_total_pages = nr_free_pagecache_pages();
writeback_set_ratelimit();
diff --git a/mm/vmscan.c b/mm/vmscan.c
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2163,6 +2163,7 @@ static int kswapd(void *p)
order = 0;
for ( ; ; ) {
unsigned long new_order;
+ int ret;
prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
new_order = pgdat->kswapd_max_order;
@@ -2174,19 +2175,23 @@ static int kswapd(void *p)
*/
order = new_order;
} else {
- if (!freezing(current))
+ if (!freezing(current) && !kthread_should_stop())
schedule();
order = pgdat->kswapd_max_order;
}
finish_wait(&pgdat->kswapd_wait, &wait);
- if (!try_to_freeze()) {
- /* We can speed up thawing tasks if we don't call
- * balance_pgdat after returning from the refrigerator
- */
+ ret = try_to_freeze();
+ if (kthread_should_stop())
+ break;
+
+ /*
+ * We can speed up thawing tasks if we don't call balance_pgdat
+ * after returning from the refrigerator
+ */
+ if (!ret)
balance_pgdat(pgdat, order);
- }
}
return 0;
}
@@ -2441,6 +2446,17 @@ int kswapd_run(int nid)
return ret;
}
+/*
+ * Called by memory hotplug when all memory in a node is offlined.
+ */
+void kswapd_stop(int nid)
+{
+ struct task_struct *kswapd = NODE_DATA(nid)->kswapd;
+
+ if (kswapd)
+ kthread_stop(kswapd);
+}
+
static int __init kswapd_init(void)
{
int nid;
--
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