The patch titled
Subject: mm: introduce dedicated WQ_MEM_RECLAIM workqueue to do lru_add_drain_all
has been added to the -mm tree. Its filename is
mm-introduce-dedicated-wq_mem_reclaim-workqueue-to-do-lru_add_drain_all.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-introduce-dedicated-wq_mem_reclaim-workqueue-to-do-lru_add_drain_all.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-introduce-dedicated-wq_mem_reclaim-workqueue-to-do-lru_add_drain_all.patch
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------------------------------------------------------
From: Wang Sheng-Hui <shhuiw@xxxxxxxxxxx>
Subject: mm: introduce dedicated WQ_MEM_RECLAIM workqueue to do lru_add_drain_all
This patch is based on https://patchwork.ozlabs.org/patch/574623/.
Tejun submitted commit 23d11a58a9a6 ("workqueue: skip flush dependency
checks for legacy workqueues") for the legacy create*_workqueue()
interface. But some workq created by alloc_workqueue still reports
warning on memory reclaim, e.g nvme_workq with flag WQ_MEM_RECLAIM set:
[ 0.153902] workqueue: WQ_MEM_RECLAIM nvme:nvme_reset_work is
flushing !WQ_MEM_RECLAIM events:lru_add_drain_per_cpu
[ 0.153907] ------------[ cut here ]------------
[ 0.153912] WARNING: CPU: 0 PID: 6 at
SoC/linux/kernel/workqueue.c:2448
check_flush_dependency+0xb4/0x10c
...
[ 0.154083] [<fffffc00080d6de0>] check_flush_dependency+0xb4/0x10c
[ 0.154088] [<fffffc00080d8e80>] flush_work+0x54/0x140
[ 0.154092] [<fffffc0008166a0c>] lru_add_drain_all+0x138/0x188
[ 0.154097] [<fffffc00081ab2dc>] migrate_prep+0xc/0x18
[ 0.154101] [<fffffc0008160e88>] alloc_contig_range+0xf4/0x350
[ 0.154105] [<fffffc00081bcef8>] cma_alloc+0xec/0x1e4
[ 0.154110] [<fffffc0008446ad0>] dma_alloc_from_contiguous+0x38/0x40
[ 0.154114] [<fffffc00080a093c>] __dma_alloc+0x74/0x25c
[ 0.154119] [<fffffc00084828d8>] nvme_alloc_queue+0xcc/0x36c
[ 0.154123] [<fffffc0008484b2c>] nvme_reset_work+0x5c4/0xda8
[ 0.154128] [<fffffc00080d9528>] process_one_work+0x128/0x2ec
[ 0.154132] [<fffffc00080d9744>] worker_thread+0x58/0x434
[ 0.154136] [<fffffc00080df0ec>] kthread+0xd4/0xe8
[ 0.154141] [<fffffc0008093ac0>] ret_from_fork+0x10/0x50
That's because lru_add_drain_all() will schedule the drain work on
system_wq, whose flag is set to 0, !WQ_MEM_RECLAIM.
Introduce a dedicated WQ_MEM_RECLAIM workqueue to do lru_add_drain_all(),
aiding in getting memory freed.
Link: http://lkml.kernel.org/r/1464917521-9775-1-git-send-email-shhuiw@xxxxxxxxxxx
Signed-off-by: Wang Sheng-Hui <shhuiw@xxxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Keith Busch <keith.busch@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thierry Reding <treding@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/swap.c | 20 +++++++++++++++++++-
1 file changed, 19 insertions(+), 1 deletion(-)
diff -puN mm/swap.c~mm-introduce-dedicated-wq_mem_reclaim-workqueue-to-do-lru_add_drain_all mm/swap.c
--- a/mm/swap.c~mm-introduce-dedicated-wq_mem_reclaim-workqueue-to-do-lru_add_drain_all
+++ a/mm/swap.c
@@ -667,6 +667,24 @@ static void lru_add_drain_per_cpu(struct
static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work);
+/*
+ * lru_add_drain_wq is used to do lru_add_drain_all() from a WQ_MEM_RECLAIM
+ * workqueue, aiding in getting memory freed.
+ */
+static struct workqueue_struct *lru_add_drain_wq;
+
+static int __init lru_init(void)
+{
+ lru_add_drain_wq = alloc_workqueue("lru-add-drain", WQ_MEM_RECLAIM, 0);
+
+ if (WARN(!lru_add_drain_wq,
+ "Failed to create workqueue lru_add_drain_wq"))
+ return -ENOMEM;
+
+ return 0;
+}
+early_initcall(lru_init);
+
void lru_add_drain_all(void)
{
static DEFINE_MUTEX(lock);
@@ -686,7 +704,7 @@ void lru_add_drain_all(void)
pagevec_count(&per_cpu(lru_deactivate_pvecs, cpu)) ||
need_activate_page_drain(cpu)) {
INIT_WORK(work, lru_add_drain_per_cpu);
- schedule_work_on(cpu, work);
+ queue_work_on(cpu, lru_add_drain_wq, work);
cpumask_set_cpu(cpu, &has_work);
}
}
_
Patches currently in -mm which might be from shhuiw@xxxxxxxxxxx are
mm-introduce-dedicated-wq_mem_reclaim-workqueue-to-do-lru_add_drain_all.patch
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