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Date: Tue, 10 Oct 2023 00:12:13 +0000
From: "Huang, Kai" <kai.huang@...el.com>
To: "hpa@...or.com" <hpa@...or.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>,
"cgroups@...r.kernel.org" <cgroups@...r.kernel.org>,
"bp@...en8.de" <bp@...en8.de>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"jarkko@...nel.org" <jarkko@...nel.org>,
"tglx@...utronix.de" <tglx@...utronix.de>,
"haitao.huang@...ux.intel.com" <haitao.huang@...ux.intel.com>,
"Mehta, Sohil" <sohil.mehta@...el.com>,
"tj@...nel.org" <tj@...nel.org>,
"mingo@...hat.com" <mingo@...hat.com>
CC: "kristen@...ux.intel.com" <kristen@...ux.intel.com>,
"yangjie@...rosoft.com" <yangjie@...rosoft.com>,
"Li, Zhiquan1" <zhiquan1.li@...el.com>,
"Christopherson,, Sean" <seanjc@...gle.com>,
"mikko.ylinen@...ux.intel.com" <mikko.ylinen@...ux.intel.com>,
"Zhang, Bo" <zhanb@...rosoft.com>,
"anakrish@...rosoft.com" <anakrish@...rosoft.com>
Subject: Re: [PATCH v5 16/18] x86/sgx: Limit process EPC usage with misc
cgroup controller
> +/**
> + * sgx_epc_cgroup_lru_empty() - check if a cgroup tree has no pages on its lrus
> + * @root: root of the tree to check
> + *
> + * Return: %true if all cgroups under the specified root have empty LRU lists.
> + * Used to avoid livelocks due to a cgroup having a non-zero charge count but
> + * no pages on its LRUs, e.g. due to a dead enclave waiting to be released or
> + * because all pages in the cgroup are unreclaimable.
> + */
> +bool sgx_epc_cgroup_lru_empty(struct sgx_epc_cgroup *root)
> +{
> + struct cgroup_subsys_state *css_root;
> + struct cgroup_subsys_state *pos;
> + struct sgx_epc_cgroup *epc_cg;
> + bool ret = true;
> +
> + /*
> + * Caller ensure css_root ref acquired
> + */
> + css_root = root ? &root->cg->css : &(misc_cg_root()->css);
> +
> + rcu_read_lock();
> + css_for_each_descendant_pre(pos, css_root) {
> + if (!css_tryget(pos))
> + break;
> +
> + rcu_read_unlock();
> +
> + epc_cg = sgx_epc_cgroup_from_misc_cg(css_misc(pos));
> +
> + spin_lock(&epc_cg->lru.lock);
> + ret = list_empty(&epc_cg->lru.reclaimable);
> + spin_unlock(&epc_cg->lru.lock);
> +
> + rcu_read_lock();
> + css_put(pos);
> + if (!ret)
> + break;
> + }
> +
> + rcu_read_unlock();
> +
> + return ret;
> +}
>
[...]
>
> static inline bool sgx_can_reclaim(void)
> {
> + if (IS_ENABLED(CONFIG_CGROUP_SGX_EPC))
> + return !sgx_epc_cgroup_lru_empty(NULL);
> +
Is it better to keep a root sgx_epc_cgroup and pass the root instead of NULL?
> return !list_empty(&sgx_global_lru.reclaimable);
> }
>
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