linux-kernel - Re: [PATCH v4 01/18] cgroup/misc: Add per resource callbacks for CSS events

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Message-Id: <CVS5O6QV7OWF.UBP59U46WUBX@suppilovahvero>
Date:   Mon, 25 Sep 2023 19:57:17 +0300
From:   "Jarkko Sakkinen" <jarkko@...nel.org>
To:     "Haitao Huang" <haitao.huang@...ux.intel.com>,
        <dave.hansen@...ux.intel.com>, <tj@...nel.org>,
        <linux-kernel@...r.kernel.org>, <linux-sgx@...r.kernel.org>,
        <x86@...nel.org>, <cgroups@...r.kernel.org>, <tglx@...utronix.de>,
        <mingo@...hat.com>, <bp@...en8.de>, <hpa@...or.com>,
        <sohil.mehta@...el.com>
Cc:     <zhiquan1.li@...el.com>, <kristen@...ux.intel.com>,
        <seanjc@...gle.com>, <zhanb@...rosoft.com>,
        <anakrish@...rosoft.com>, <mikko.ylinen@...ux.intel.com>,
        <yangjie@...rosoft.com>
Subject: Re: [PATCH v4 01/18] cgroup/misc: Add per resource callbacks for
 CSS events

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@...nel.org>  
> wrote:
>
> > On Wed Sep 13, 2023 at 7:06 AM EEST, Haitao Huang wrote:
> >> From: Kristen Carlson Accardi <kristen@...ux.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. Add
> >
> > 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 resource  
> type specific action for Cgroups Subsystem State (CSS) events: the  
> 'css_alloc' event when a cgroup is created and the 'css_free' event when a  
> cgroup is destroyed, or in event of user writing the max value to the  
> misc.max file to set the consumption limit of a specific resource  
> [admin-guide/cgroup-v2.rst, 5-9. Misc].
>
> Define callbacks for those events and allow resource providers to register  
> the callbacks per resource type as needed. This will be utilized later by  
> the EPC misc cgroup support implemented in the SGX driver:
> - On cgroup alloc, allocate and initialize necessary structures for EPC  
> 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  
> current consumption.

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

> Thanks
> Haitao

BR, Jarkko