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Date:   Mon, 25 Sep 2023 19:57:17 +0300
Message-Id: <CVS5O6QV7OWF.UBP59U46WUBX@suppilovahvero>
Cc:     <zhiquan1.li@intel.com>, <kristen@linux.intel.com>,
        <seanjc@google.com>, <zhanb@microsoft.com>,
        <anakrish@microsoft.com>, <mikko.ylinen@linux.intel.com>,
        <yangjie@microsoft.com>
Subject: Re: [PATCH v4 01/18] cgroup/misc: Add per resource callbacks for
 CSS events
From:   "Jarkko Sakkinen" <jarkko@kernel.org>
To:     "Haitao Huang" <haitao.huang@linux.intel.com>,
        <dave.hansen@linux.intel.com>, <tj@kernel.org>,
        <linux-kernel@vger.kernel.org>, <linux-sgx@vger.kernel.org>,
        <x86@kernel.org>, <cgroups@vger.kernel.org>, <tglx@linutronix.de>,
        <mingo@redhat.com>, <bp@alien8.de>, <hpa@zytor.com>,
        <sohil.mehta@intel.com>
References: <20230913040635.28815-1-haitao.huang@linux.intel.com>
 <20230913040635.28815-2-haitao.huang@linux.intel.com>
 <CVHOU5G1SCUT.RCBVZ3W8G2NJ@suppilovahvero>
 <op.2bci9anpwjvjmi@hhuan26-mobl.amr.corp.intel.com>
In-Reply-To: <op.2bci9anpwjvjmi@hhuan26-mobl.amr.corp.intel.com>
Precedence: bulk

On Sat Sep 16, 2023 at 7:11 AM EEST, Haitao Huang wrote:
> Hi Jarkko
>
> On Wed, 13 Sep 2023 04:39:06 -0500, Jarkko Sakkinen <jarkko@kernel.org> =
=20
> wrote:
>
> > On Wed Sep 13, 2023 at 7:06 AM EEST, Haitao Huang wrote:
> >> From: Kristen Carlson Accardi <kristen@linux.intel.com>
> >>
> >> Consumers of the misc cgroup controller might need to perform separate
> >> actions for Cgroups Subsystem State(CSS) events: cgroup alloc and free=
.
> >
> > nit: s/State(CSS)/State (CSS)/
> >
> > "cgroup alloc" and "cgroup free" mean absolutely nothing.
> >
> >
> >> In addition, writes to the max value may also need separate action. Ad=
d
> >
> > What "the max value"?
> >
> >> the ability to allow downstream users to setup callbacks for these
> >> operations, and call the corresponding per-resource-type callback when
> >> appropriate.
> >
> > Who are "the downstream users" and what sort of callbacks they setup?
>
> How about this?
>
> The misc cgroup controller (subsystem) currently does not perform resourc=
e =20
> type specific action for Cgroups Subsystem State (CSS) events: the =20
> 'css_alloc' event when a cgroup is created and the 'css_free' event when =
a =20
> cgroup is destroyed, or in event of user writing the max value to the =20
> misc.max file to set the consumption limit of a specific resource =20
> [admin-guide/cgroup-v2.rst, 5-9. Misc].
>
> Define callbacks for those events and allow resource providers to registe=
r =20
> the callbacks per resource type as needed. This will be utilized later by=
 =20
> the EPC misc cgroup support implemented in the SGX driver:
> - On cgroup alloc, allocate and initialize necessary structures for EPC =
=20
> reclaiming, e.g., LRU list, work queue, etc.
> - On cgroup free, cleanup and free those structures created in alloc.
> - On max write, trigger EPC reclaiming if the new limit is at or below =
=20
> current consumption.

Yeah, this is much better (I was on holiday, thus the delay on
response).

> Thanks
> Haitao

BR, Jarkko