Commit ab5cdc31 authored Oct 21, 2015 by Leon Romanovsky Committed by Doug Ledford Dec 08, 2015

IB/mlx5: Postpone remove_keys under knowledge of coming preemption



The remove_keys() logic is performed as garbage collection task. Such
task is intended to be run when no other active processes are running.

The need_resched() will return TRUE if there are user tasks to be
activated in near future.

In such case, we don't execute remove_keys() and postpone
the garbage collection work to try to run in next cycle,
in order to free CPU resources to other tasks.

The possible pseudo-code to trigger such scenario:
1. Allocate a lot of MR to fill the cache above the limit.
2. Wait a small amount of time "to calm" the system.
3. Start CPU extensive operations on multi-node cluster.
4. Expect performance degradation during MR cache shrink operation.

Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Eli Cohen <eli@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

parent 0ef2f05c

drivers/infiniband/hw/mlx5/mr.c

+13 −1

Original line number	Diff line number	Diff line
		@@ -381,7 +381,19 @@ static void __cache_work_func(struct mlx5_cache_ent *ent)
		}
		}
		} else if (ent->cur > 2 * ent->limit) {
		if (!someone_adding(cache) &&
		/*
		* The remove_keys() logic is performed as garbage collection
		* task. Such task is intended to be run when no other active
		* processes are running.
		*
		* The need_resched() will return TRUE if there are user tasks
		* to be activated in near future.
		*
		* In such case, we don't execute remove_keys() and postpone
		* the garbage collection work to try to run in next cycle,
		* in order to free CPU resources to other tasks.
		*/
		if (!need_resched() && !someone_adding(cache) &&
		time_after(jiffies, cache->last_add + 300 * HZ)) {
		remove_keys(dev, i, 1);
		if (ent->cur > ent->limit)