On Thu, May 27, 2021 at 4:52 AM Shakeel Butt [off-list ref] wrote:

Adding linux-mm and related folks.



On Wed, May 26, 2021 at 9:18 AM [off-list ref] wrote:

quoted

From: Yulei Zhang <redacted>

In this patch set we present the idea to suppress the memory allocation
speed in memory cgroup, which aims to avoid direct reclaim caused by
memory allocation burst while under memory pressure.

I am assuming here direct reclaim means global reclaim.

Yep.

quoted

As minimum watermark could be easily broken if certain tasks allocate
massive amount of memory in a short period of time, in that case it will
trigger the direct memory reclaim and cause unacceptable jitters for
latency critical tasks, such as guaranteed pod task in K8s.

With memory allocation speed throttle(mst) mechanism we could lower the
memory allocation speed in certian cgroup, usually for low priority tasks,
so that could avoid the direct memory reclaim in time.

Can you please explain why memory.high is not good enough for your
use-case? You can orchestrate the memory.high limits in such a way
that those certain cgroups hit their memory.high limit before causing
the global reclaim. You might need to dynamically adjust the limits
based on other workloads or unaccounted memory.

Yep, dynamically adjust the memory.high limits can ease the memory pressure
and postpone the global reclaim, but it can easily trigger the oom in
the cgroups,
which may not be suitable in certain usage cases when we want the services
alive. Using throttle to suppress the allocation may help keep the
activities and
doesn't impact others.  Thanks.

quoted

And per-memcg interfaces are introduced under memcg tree, not visiable for
root memcg.
- <cgroup_root>/<cgroup_name>/memory.alloc_bps
 - 0 -> means memory speed throttle disabled
 - non-zero -> value in bytes for memory allocation speed limits

- <cgroup_root>/<cgroup_name>/memory.stat:mst_mem_spd_max
  it records the max memory allocation speed of the memory cgroup in the
  last period of time slice

- <cgroup_root>/<cgroup_name>/memory.stat:mst_nr_throttled
  it represents the number of times for allocation throttling

Yulei Zhang (7):
  mm: record total charge and max speed counter in memcg
  mm: introduce alloc_bps to memcg for memory allocation speed throttle
  mm: memory allocation speed throttle setup in hierarchy
  mm: introduce slice analysis into memory speed throttle mechanism
  mm: introduce memory allocation speed throttle
  mm: record the numbers of memory allocation throttle
  mm: introduce mst low and min watermark

 include/linux/memcontrol.h   |  23 +++
 include/linux/page_counter.h |   8 +
 init/Kconfig                 |   8 +
 mm/memcontrol.c              | 295 +++++++++++++++++++++++++++++++++++
 mm/page_counter.c            |  39 +++++
 5 files changed, 373 insertions(+)

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2.28.0