linux-kernel - Re: [PATCH v16 08/16] x86/sgx: Encapsulate uses of the global LRU

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Message-ID: <b91e6636ab7b6b96a723c9ea78ad5119ea1502c9.camel@intel.com>
Date: Tue, 27 Aug 2024 11:13:41 +0000
From: "Huang, Kai" <kai.huang@...el.com>
To: "chenridong@...wei.com" <chenridong@...wei.com>,
	"linux-sgx@...r.kernel.org" <linux-sgx@...r.kernel.org>,
	"cgroups@...r.kernel.org" <cgroups@...r.kernel.org>, "mkoutny@...e.com"
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	<dave.hansen@...ux.intel.com>, "haitao.huang@...ux.intel.com"
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	"jarkko@...nel.org" <jarkko@...nel.org>, "Mehta, Sohil"
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CC: "mikko.ylinen@...ux.intel.com" <mikko.ylinen@...ux.intel.com>,
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	<yangjie@...rosoft.com>, "Li, Zhiquan1" <zhiquan1.li@...el.com>,
	"chrisyan@...rosoft.com" <chrisyan@...rosoft.com>
Subject: Re: [PATCH v16 08/16] x86/sgx: Encapsulate uses of the global LRU


> +static inline bool sgx_can_reclaim_global(void)
> +{
> +	/*
> +	 * Now all EPC pages are still tracked in the @sgx_global_lru, so only
> +	 * check @sgx_global_lru.
> +	 *
> +	 * When EPC pages are tracked in the actual per-cgroup LRUs,
> +	 * replace with sgx_cgroup_lru_empty(misc_cg_root()).
> +	 */
> +	return !list_empty(&sgx_global_lru.reclaimable);
> +}

Firstly, sgx_cgroup_lru_empty() is only introduced in the next patch, so it's
wrong to mention it in the comment in _this_ patch.

It's weird to add the above comment here in this patch anyway, since ...

[...]


> +static void sgx_reclaim_pages_global(void)
> +{
> +	sgx_reclaim_pages(&sgx_global_lru);
>  }

... this function (which is no difference IMHO) doesn't have a similar comment
here.

The similar comment to this function is only added in the later "[PATCH v16
12/16] x86/sgx: Revise global reclamation for EPC cgroups":

 static void sgx_reclaim_pages_global(struct mm_struct *charge_mm)
 {
+	/*
+	 * Now all EPC pages are still tracked in the @sgx_global_lru.
+	 * Still reclaim from it.
+	 *
+	 * When EPC pages are tracked in the actual per-cgroup LRUs,
+	 * sgx_cgroup_reclaim_pages_global() will be called.
+	 */
 	sgx_reclaim_pages(&sgx_global_lru, charge_mm);
 }

So if the comment of sgx_can_reclaim_global() were needed, it's more
reasonable to add it in the later patch where the comment for
sgx_reclaim_pages_global() is also added IMHO?