The patch titled
Subject: mm/memcg: prepare for swap over-high accounting and penalty calculation
has been added to the -mm tree. Its filename is
mm-prepare-for-swap-over-high-accounting-and-penalty-calculation.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-prepare-for-swap-over-high-accounting-and-penalty-calculation.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-prepare-for-swap-over-high-accounting-and-penalty-calculation.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Jakub Kicinski <kuba@xxxxxxxxxx>
Subject: mm/memcg: prepare for swap over-high accounting and penalty calculation
Patch series "memcg: Slow down swap allocation as the available space gets
depleted", v6.
Tejun describes the problem as follows:
When swap runs out, there's an abrupt change in system behavior - the
anonymous memory suddenly becomes unmanageable which readily breaks any
sort of memory isolation and can bring down the whole system. To avoid
that, oomd [1] monitors free swap space and triggers kills when it drops
below the specific threshold (e.g. 15%).
While this works, it's far from ideal:
- Depending on IO performance and total swap size, a given
headroom might not be enough or too much.
- oomd has to monitor swap depletion in addition to the usual
pressure metrics and it currently doesn't consider memory.swap.max.
Solve this by adapting parts of the approach that memory.high uses - slow
down allocation as the resource gets depleted turning the depletion
behavior from abrupt cliff one to gradual degradation observable through
memory pressure metric.
[1] https://github.com/facebookincubator/oomd
This patch (of 4):
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().
Link: http://lkml.kernel.org/r/20200527195846.102707-1-kuba@xxxxxxxxxx
Link: http://lkml.kernel.org/r/20200527195846.102707-2-kuba@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Chris Down <chris@xxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memcontrol.c | 62 +++++++++++++++++++++++++---------------------
1 file changed, 35 insertions(+), 27 deletions(-)
--- a/mm/memcontrol.c~mm-prepare-for-swap-over-high-accounting-and-penalty-calculation
+++ a/mm/memcontrol.c
@@ -2321,41 +2321,48 @@ static void high_work_func(struct work_s
#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;
+ u64 overage;
- do {
- unsigned long usage, high;
- u64 overage;
+ if (usage <= high)
+ return 0;
- usage = page_counter_read(&memcg->memory);
- high = READ_ONCE(memcg->high);
+ /*
+ * Prevent division by 0 in overage calculation by acting as if
+ * it was a threshold of 1 page
+ */
+ high = max(high, 1UL);
- if (usage <= high)
- continue;
+ overage = usage - high;
+ overage <<= MEMCG_DELAY_PRECISION_SHIFT;
+ return div64_u64(overage, high);
+}
- /*
- * 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;
- 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;
@@ -2411,7 +2418,8 @@ 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
_
Patches currently in -mm which might be from kuba@xxxxxxxxxx are
mm-prepare-for-swap-over-high-accounting-and-penalty-calculation.patch
mm-move-penalty-delay-clamping-out-of-calculate_high_delay.patch
mm-move-cgroup-high-memory-limit-setting-into-struct-page_counter.patch
mm-automatically-penalize-tasks-with-high-swap-use.patch
