linux-kernel - Re: [PATCH 0/2] Support hugetlb charge moving at task migration

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Message-ID: <YVWVk559nm2xZ98R@dhcp22.suse.cz>
Date:   Thu, 30 Sep 2021 12:46:43 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Baolin Wang <baolin.wang@...ux.alibaba.com>
Cc:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] Support hugetlb charge moving at task migration

On Wed 29-09-21 18:19:26, Baolin Wang wrote:
> Hi,
> 
> Now in the hugetlb cgroup, charges associated with a task aren't moved
> to the new hugetlb cgroup at task migration, which is odd for hugetlb
> cgroup usage.

Could you elaborate some more about the usecase and/or problems you see
with the existing semantic?

> This patch set adds hugetlb cgroup charge moving when
> migrate tasks among cgroups, which are based on the memcg charge moving.

Memcg charge moving has shown some problems over time and hence this is
not part of cgroup v2 interface anymore. Even for cgroup v1 this has
been an opt-in. I do not see anything like that in this patch series.
Why should all existing workloads follow a different semantic during
task migration now?

> Please help to review. Thanks.
> 
> Baolin Wang (2):
>   hugetlb_cgroup: Add interfaces to move hugetlb charge at task
>     migration
>   hugetlb_cgroup: Add post_attach interface for tasks migration
> 
>  mm/hugetlb_cgroup.c | 230 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 230 insertions(+)
> 
> -- 
> 1.8.3.1

-- 
Michal Hocko
SUSE Labs