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From: Waiman Long <longman@redhat.com>
To: Andrew Morton <akpm@linux-foundation.org>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Michal Hocko <mhocko@kernel.org>,
	Vladimir Davydov <vdavydov.dev@gmail.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	Ingo Molnar <mingo@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>
Cc: linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, cgroups@vger.kernel.org,
	linux-mm@kvack.org, Waiman Long <longman@redhat.com>
Subject: [RFC PATCH 6/8] memcg: Introduce additional memory control slowdown if needed
Date: Mon, 17 Aug 2020 10:08:29 -0400	[thread overview]
Message-ID: <20200817140831.30260-7-longman@redhat.com> (raw)
In-Reply-To: <20200817140831.30260-1-longman@redhat.com>

For fast cpus on slow disks, yielding the cpus repeatedly with
PR_MEMACT_SLOWDOWN may not be able to slow down memory allocation enough
for memory reclaim to catch up. In case a large memory block is mmap'ed
and the pages are faulted in one-by-one, the syscall delays won't be
activated during this process.

To be safe, an additional variable delay of 20-5000 us will be added
to __mem_cgroup_over_high_action() if the excess memory used is more
than 1/256 of the memory limit.

Signed-off-by: Waiman Long <longman@redhat.com>
---
 mm/memcontrol.c | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 6488f8a10d66..bddf3e659469 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2643,11 +2643,10 @@ get_rss_counter(struct mm_struct *mm, int mm_bit, u16 flags, int rss_bit)
 static bool __mem_cgroup_over_high_action(struct mem_cgroup *memcg, u8 action,
 					  u16 flags)
 {
-	unsigned long mem = 0;
+	unsigned long mem = 0, limit = 0, excess = 0;
 	bool ret = false;
 	struct mm_struct *mm = get_task_mm(current);
 	u8  signal = READ_ONCE(current->memcg_over_high_signal);
-	u32 limit;
 
 	if (!mm)
 		return true;	/* No more check is needed */
@@ -2657,9 +2656,10 @@ static bool __mem_cgroup_over_high_action(struct mem_cgroup *memcg, u8 action,
 
 	if (memcg) {
 		mem = page_counter_read(&memcg->memory);
-		limit = READ_ONCE(current->memcg_over_high_climit);
-		if (mem <= memcg->memory.high + limit)
+		limit = READ_ONCE(current->memcg_over_high_climit) + memcg->memory.high;
+		if (mem <= limit)
 			goto out;
+		excess = mem - limit;
 	}
 
 	/*
@@ -2676,6 +2676,7 @@ static bool __mem_cgroup_over_high_action(struct mem_cgroup *memcg, u8 action,
 		limit = READ_ONCE(current->memcg_over_high_plimit);
 		if (mem <= limit)
 			goto out;
+		excess = mem - limit;
 	}
 
 	ret = true;
@@ -2685,10 +2686,19 @@ static bool __mem_cgroup_over_high_action(struct mem_cgroup *memcg, u8 action,
 		break;
 	case PR_MEMACT_SLOWDOWN:
 		/*
-		 * Slow down by yielding the cpu & adding delay to
-		 * memory allocation syscalls.
+		 * Slow down by yielding the cpu & adding delay to memory
+		 * allocation syscalls.
+		 *
+		 * An additional 20-5000 us of delay is added in case the
+		 * excess memory is more than 1/256 of the limit.
 		 */
 		WRITE_ONCE(current->memcg_over_limit, true);
+		limit >>= 8;
+		if (limit && (excess > limit)) {
+			int delay = min(5000UL, excess/limit * 20UL);
+
+			udelay(delay);
+		}
 		set_tsk_need_resched(current);
 		set_preempt_need_resched();
 		break;
-- 
2.18.1


  parent reply	other threads:[~2020-08-17 14:10 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-17 14:08 [RFC PATCH 0/8] memcg: Enable fine-grained per process memory control Waiman Long
2020-08-17 14:08 ` [RFC PATCH 1/8] memcg: Enable fine-grained control of over memory.high action Waiman Long
2020-08-17 14:30   ` Chris Down
2020-08-17 15:38     ` Waiman Long
2020-08-17 16:11       ` Chris Down
2020-08-17 16:44   ` Shakeel Butt
2020-08-17 16:56     ` Chris Down
2020-08-18 19:12       ` Waiman Long
2020-08-18 19:14     ` Waiman Long
2020-08-17 14:08 ` [RFC PATCH 2/8] memcg, mm: Return ENOMEM or delay if memcg_over_limit Waiman Long
2020-08-17 14:08 ` [RFC PATCH 3/8] memcg: Allow the use of task RSS memory as over-high action trigger Waiman Long
2020-08-17 14:08 ` [RFC PATCH 4/8] fs/proc: Support a new procfs memctl file Waiman Long
2020-08-17 14:08 ` [RFC PATCH 5/8] memcg: Allow direct per-task memory limit checking Waiman Long
2020-08-17 14:08 ` Waiman Long [this message]
2020-08-17 14:08 ` [RFC PATCH 7/8] memcg: Enable logging of memory control mitigation action Waiman Long
2020-08-17 14:08 ` [RFC PATCH 8/8] memcg: Add over-high action prctl() documentation Waiman Long
2020-08-17 15:26 ` [RFC PATCH 0/8] memcg: Enable fine-grained per process memory control Michal Hocko
2020-08-17 15:55   ` Waiman Long
2020-08-17 19:26     ` Michal Hocko
2020-08-18 19:20       ` Waiman Long
2020-08-18  9:14 ` peterz
2020-08-18  9:26   ` Michal Hocko
2020-08-18  9:59     ` peterz
2020-08-18 10:05       ` Michal Hocko
2020-08-18 10:18         ` peterz
2020-08-18 10:30           ` Michal Hocko
2020-08-18 10:36             ` peterz
2020-08-18 13:49           ` Johannes Weiner
2020-08-21 19:37             ` Peter Zijlstra
2020-08-24 16:58               ` Johannes Weiner
2020-09-07 11:47                 ` Chris Down
2020-09-09 11:53                 ` Michal Hocko
2020-08-18 10:17       ` Chris Down
2020-08-18 10:26         ` peterz
2020-08-18 10:35           ` Chris Down
2020-08-23  2:49         ` Waiman Long
2020-08-18  9:27   ` Chris Down
2020-08-18 10:04     ` peterz
2020-08-18 12:55       ` Matthew Wilcox
2020-08-20  6:11         ` Dave Chinner
2020-08-18 19:30     ` Waiman Long
2020-08-18 19:27   ` Waiman Long

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