[PATCH mm v5 RESEND 1/4] mm: prepare for swap over-high accounting and penalty calculation

Jakub Kicinski
2020-05-21T00:24:16Z

Slice the memory overage calculation logic a little bit so we can
reuse it to apply a similar penalty to the swap. The logic which
accesses the memory-specific fields (use and high values) has to
be taken out of calculate_high_delay().

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
---
mm/memcontrol.c | 62 ++++++++++++++++++++++++++++---------------------
1 file changed, 35 insertions(+), 27 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 2df9510b7d64..0d05e6a593f5 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2302,41 +2302,48 @@ static void high_work_func(struct work_struct *work)
#define MEMCG_DELAY_PRECISION_SHIFT 20
#define MEMCG_DELAY_SCALING_SHIFT 14

-/*
- * Get the number of jiffies that we should penalise a mischievous cgroup which
- * is exceeding its memory.high by checking both it and its ancestors.
- */
-static unsigned long calculate_high_delay(struct mem_cgroup *memcg,
- unsigned int nr_pages)
+static u64 calculate_overage(unsigned long usage, unsigned long high)
{
- unsigned long penalty_jiffies;
- u64 max_overage = 0;
-
- do {
- unsigned long usage, high;
- u64 overage;
+ u64 overage;

- usage = page_counter_read(&memcg->memory);
- high = READ_ONCE(memcg->high);
+ if (usage <= high)
+ return 0;

- if (usage <= high)
- continue;
+ /*
+ * Prevent division by 0 in overage calculation by acting as if
+ * it was a threshold of 1 page
+ */
+ high = max(high, 1UL);

- /*
- * Prevent division by 0 in overage calculation by acting as if
- * it was a threshold of 1 page
- */
- high = max(high, 1UL);
+ overage = usage - high;
+ overage <<= MEMCG_DELAY_PRECISION_SHIFT;
+ return div64_u64(overage, high);
+}

- overage = usage - high;
- overage <<= MEMCG_DELAY_PRECISION_SHIFT;
- overage = div64_u64(overage, high);
+static u64 mem_find_max_overage(struct mem_cgroup *memcg)
+{
+ u64 overage, max_overage = 0;

- if (overage > max_overage)
- max_overage = overage;
+ do {
+ overage = calculate_overage(page_counter_read(&memcg->memory),
+ READ_ONCE(memcg->high));
+ max_overage = max(overage, max_overage);
} while ((memcg = parent_mem_cgroup(memcg)) &&
!mem_cgroup_is_root(memcg));

+ return max_overage;
+}
+
+/*
+ * Get the number of jiffies that we should penalise a mischievous cgroup which
+ * is exceeding its memory.high by checking both it and its ancestors.
+ */
+static unsigned long calculate_high_delay(struct mem_cgroup *memcg,
+ unsigned int nr_pages,
+ u64 max_overage)
+{
+ unsigned long penalty_jiffies;
+
if (!max_overage)
return 0;

@@ -2392,7 +2399,8 @@ void mem_cgroup_handle_over_high(void)
* memory.high is breached and reclaim is unable to keep up. Throttle
* allocators proactively to slow down excessive growth.
*/
- penalty_jiffies = calculate_high_delay(memcg, nr_pages);
+ penalty_jiffies = calculate_high_delay(memcg, nr_pages,
+ mem_find_max_overage(memcg));

/*
* Don't sleep if the amount of jiffies this memcg owes us is so low
--
2.25.4