Re: [RFC 0/7] Introduce memory allocation speed throttle in memcg

[Shakeel Butt <shakeelb@google.com>]

Adding linux-mm and related folks.



On Wed, May 26, 2021 at 9:18 AM <yulei.kernel@gmail.com> wrote:
>
> From: Yulei Zhang <yuleixzhang@tencent.com>
>
> 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.

> 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.

>
> 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(+)
>
> --
> 2.28.0
>