From: "Haitao Huang" <haitao.huang@linux.intel.com>
To: "jarkko@kernel.org" <jarkko@kernel.org>,
"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
"tj@kernel.org" <tj@kernel.org>,
"mkoutny@suse.com" <mkoutny@suse.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-sgx@vger.kernel.org" <linux-sgx@vger.kernel.org>,
"x86@kernel.org" <x86@kernel.org>,
"cgroups@vger.kernel.org" <cgroups@vger.kernel.org>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"mingo@redhat.com" <mingo@redhat.com>,
"bp@alien8.de" <bp@alien8.de>, "hpa@zytor.com" <hpa@zytor.com>,
"Mehta, Sohil" <sohil.mehta@intel.com>,
"Huang, Kai" <kai.huang@intel.com>
Cc: "Li, Zhiquan1" <zhiquan1.li@intel.com>,
"kristen@linux.intel.com" <kristen@linux.intel.com>,
"seanjc@google.com" <seanjc@google.com>,
"Zhang, Bo" <zhanb@microsoft.com>,
"anakrish@microsoft.com" <anakrish@microsoft.com>,
"mikko.ylinen@linux.intel.com" <mikko.ylinen@linux.intel.com>,
"yangjie@microsoft.com" <yangjie@microsoft.com>,
"chrisyan@microsoft.com" <chrisyan@microsoft.com>
Subject: Re: [PATCH v8 04/15] x86/sgx: Implement basic EPC misc cgroup functionality
Date: Tue, 30 Jan 2024 19:59:26 -0600 [thread overview]
Message-ID: <op.2id2hcvkwjvjmi@hhuan26-mobl.amr.corp.intel.com> (raw)
In-Reply-To: <BL1PR11MB59784620554CDAD5E2C2BF45F77D2@BL1PR11MB5978.namprd11.prod.outlook.com>
On Tue, 30 Jan 2024 09:22:14 -0600, Huang, Kai <kai.huang@intel.com> wrote:
>> struct sgx_epc_page *sgx_alloc_epc_page(void *owner, bool reclaim) {
>> + struct sgx_epc_cgroup *epc_cg;
>> struct sgx_epc_page *page;
>> + int ret;
>> +
>> + epc_cg = sgx_get_current_epc_cg();
>> + ret = sgx_epc_cgroup_try_charge(epc_cg);
>> + if (ret) {
>> + sgx_put_epc_cg(epc_cg);
>> + return ERR_PTR(ret);
>> + }
>>
>> for ( ; ; ) {
>> page = __sgx_alloc_epc_page();
>> @@ -567,8 +578,10 @@ struct sgx_epc_page *sgx_alloc_epc_page(void
>> *owner, bool reclaim)
>> break;
>> }
>>
>> - if (list_empty(&sgx_active_page_list))
>> - return ERR_PTR(-ENOMEM);
>> + if (list_empty(&sgx_active_page_list)) {
>> + page = ERR_PTR(-ENOMEM);
>> + break;
>> + }
>
> (Sorry for replying from Outlook because I am in travel for Chinese New
> Year.)
>
> Perhaps I am missing something but I don't understand this change.
>
> An empty sgx_active_page_list means you cannot reclaim any page from it,
> so why need to break?
>
This is to avoid any escape for sgx_put_epc_cg(), which is added in this
version.
>>
>> if (!reclaim) {
>> page = ERR_PTR(-EBUSY);
>> @@ -580,10 +593,25 @@ struct sgx_epc_page *sgx_alloc_epc_page(void
>> *owner, bool reclaim)
>> break;
>> }
>>
>> + /*
>> + * Need to do a global reclamation if cgroup was not full but
>> free
>> + * physical pages run out, causing __sgx_alloc_epc_page() to
>> fail.
>> + */
>> sgx_reclaim_pages();
>> cond_resched();
>> }
>
> And why adding this comment, especially in this patch?
>
> I don't see it brings additional clarity because there's only global
> reclaim now, no matter whether cgroup is enabled or not.
>
True there is only global reclamation at the moment. The comment intended
to help clarify why we can get here when try_charge() passes. It at least
took me some thinking to realize that fact so I put it here to help remind
this can happen even for cases that try_charge() passes. (In some earlier
debugging for some concurrent issues, I actually tried mistakenly to
remove this path hoping to narrow down some causes but made situation
worse.)
I can remove if no one thinks this is needed.
Thanks
Haitao
next prev parent reply other threads:[~2024-01-31 1:59 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-30 2:09 [PATCH v8 00/15] Add Cgroup support for SGX EPC memory Haitao Huang
2024-01-30 2:09 ` [PATCH v8 01/15] cgroup/misc: Add per resource callbacks for CSS events Haitao Huang
2024-02-01 23:24 ` Jarkko Sakkinen
2024-02-02 16:34 ` Haitao Huang
2024-02-02 17:02 ` Tejun Heo
2024-02-12 19:31 ` Jarkko Sakkinen
2024-01-30 2:09 ` [PATCH v8 02/15] cgroup/misc: Export APIs for SGX driver Haitao Huang
2024-01-30 2:09 ` [PATCH v8 03/15] cgroup/misc: Add SGX EPC resource type Haitao Huang
2024-01-30 2:09 ` [PATCH v8 04/15] x86/sgx: Implement basic EPC misc cgroup functionality Haitao Huang
2024-01-30 15:22 ` Huang, Kai
2024-01-31 1:59 ` Haitao Huang [this message]
2024-02-01 23:27 ` Jarkko Sakkinen
2024-01-30 2:09 ` [PATCH v8 05/15] x86/sgx: Add sgx_epc_lru_list to encapsulate LRU list Haitao Huang
2024-02-01 23:28 ` Jarkko Sakkinen
2024-02-02 16:52 ` Haitao Huang
2024-01-30 2:09 ` [PATCH v8 06/15] x86/sgx: Abstract tracking reclaimable pages in LRU Haitao Huang
2024-02-01 23:29 ` Jarkko Sakkinen
2024-01-30 2:09 ` [PATCH v8 07/15] x86/sgx: Expose sgx_reclaim_pages() for cgroup Haitao Huang
2024-01-30 15:39 ` Huang, Kai
2024-01-31 1:35 ` Haitao Huang
2024-02-01 23:37 ` Jarkko Sakkinen
2024-01-30 2:09 ` [PATCH v8 08/15] x86/sgx: Implement EPC reclamation flows " Haitao Huang
2024-02-01 23:39 ` Jarkko Sakkinen
2024-01-30 2:09 ` [PATCH v8 09/15] x86/sgx: Charge mem_cgroup for per-cgroup reclamation Haitao Huang
2024-01-30 2:09 ` [PATCH v8 10/15] x86/sgx: Add EPC reclamation in cgroup try_charge() Haitao Huang
2024-01-30 2:09 ` [PATCH v8 11/15] x86/sgx: Abstract check for global reclaimable pages Haitao Huang
2024-01-30 2:09 ` [PATCH v8 12/15] x86/sgx: Expose sgx_epc_cgroup_reclaim_pages() for global reclaimer Haitao Huang
2024-01-30 2:09 ` [PATCH v8 13/15] x86/sgx: Turn on per-cgroup EPC reclamation Haitao Huang
2024-01-30 2:09 ` [PATCH v8 14/15] Docs/x86/sgx: Add description for cgroup support Haitao Huang
2024-01-30 2:09 ` [PATCH v8 15/15] selftests/sgx: Add scripts for EPC cgroup testing Haitao Huang
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