linux-kernel - Re: [PATCH v12 12/14] x86/sgx: Turn on per-cgroup EPC reclamation

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Date: Mon, 29 Apr 2024 20:31:21 -0500
From: "Haitao Huang" <haitao.huang@...ux.intel.com>
To: "hpa@...or.com" <hpa@...or.com>, "tim.c.chen@...ux.intel.com"
 <tim.c.chen@...ux.intel.com>, "linux-sgx@...r.kernel.org"
 <linux-sgx@...r.kernel.org>, "x86@...nel.org" <x86@...nel.org>,
 "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
 "jarkko@...nel.org" <jarkko@...nel.org>, "cgroups@...r.kernel.org"
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 <linux-kernel@...r.kernel.org>, "mkoutny@...e.com" <mkoutny@...e.com>,
 "tglx@...utronix.de" <tglx@...utronix.de>, "Mehta, Sohil"
 <sohil.mehta@...el.com>, "tj@...nel.org" <tj@...nel.org>, "mingo@...hat.com"
 <mingo@...hat.com>, "bp@...en8.de" <bp@...en8.de>, "Huang, Kai"
 <kai.huang@...el.com>
Cc: "mikko.ylinen@...ux.intel.com" <mikko.ylinen@...ux.intel.com>,
 "seanjc@...gle.com" <seanjc@...gle.com>, "anakrish@...rosoft.com"
 <anakrish@...rosoft.com>, "Zhang, Bo" <zhanb@...rosoft.com>,
 "kristen@...ux.intel.com" <kristen@...ux.intel.com>, "yangjie@...rosoft.com"
 <yangjie@...rosoft.com>, "Li, Zhiquan1" <zhiquan1.li@...el.com>,
 "chrisyan@...rosoft.com" <chrisyan@...rosoft.com>
Subject: Re: [PATCH v12 12/14] x86/sgx: Turn on per-cgroup EPC reclamation

On Mon, 29 Apr 2024 17:18:05 -0500, Huang, Kai <kai.huang@...el.com> wrote:

>
>>>>  /*
>>>> @@ -42,7 +63,8 @@ static inline struct sgx_epc_lru_list  
>>>> *sgx_lru_list(struct sgx_epc_page *epc_pag
>>>>   */
>>>>  static inline bool sgx_can_reclaim(void)
>>>>  {
>>>> -    return !list_empty(&sgx_global_lru.reclaimable);
>>>> +    return !sgx_cgroup_lru_empty(misc_cg_root()) ||
>>>> +           !list_empty(&sgx_global_lru.reclaimable);
>>>>  }
>>>
>>> Shouldn't this be:
>>>
>>>     if (IS_ENABLED(CONFIG_CGROUP_MISC))
>>>         return !sgx_cgroup_lru_empty(misc_cg_root());
>>>     else
>>>         return !list_empty(&sgx_global_lru.reclaimable);
>>> ?
>>>
>>> In this way, it is consistent with the sgx_reclaim_pages_global()  
>>> below.
>>>
>>  I changed to this way because sgx_cgroup_lru_empty() is now defined in  
>> both KConfig cases.
>> And it seems better to minimize use of the KConfig variables based on  
>> earlier feedback (some are yours).
>> Don't really have strong preference here. So let me know one way of the  
>> other.
>>
>
> But IMHO your code could be confusing, e.g., it can be interpreted as:
>
>    The EPC pages can be managed by both the cgroup LRUs and the
>    sgx_global_lru simultaneously at runtime when CONFIG_CGROUP_MISC
>    is on.
>
> Which is not true.
>
> So we should make the code clearly reflect the true behaviour.
>

Ok, I'll change back.
Thanks
Haitao