From: "Haitao Huang" <haitao.huang@linux.intel.com>
To: jarkko@kernel.org, dave.hansen@linux.intel.com, tj@kernel.org,
mkoutny@suse.com, linux-kernel@vger.kernel.org,
linux-sgx@vger.kernel.org, x86@kernel.org,
cgroups@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com,
bp@alien8.de, hpa@zytor.com, sohil.mehta@intel.com,
"Dave Hansen" <dave.hansen@intel.com>
Cc: zhiquan1.li@intel.com, kristen@linux.intel.com,
seanjc@google.com, zhanb@microsoft.com, anakrish@microsoft.com,
mikko.ylinen@linux.intel.com, yangjie@microsoft.com
Subject: Re: [PATCH v6 00/12] Add Cgroup support for SGX EPC memory
Date: Fri, 05 Jan 2024 14:13:31 -0600 [thread overview]
Message-ID: <op.2g3bstxxwjvjmi@hhuan26-mobl.amr.corp.intel.com> (raw)
In-Reply-To: <772cb101-33e3-4b55-a311-142b22575e7c@intel.com>
On Fri, 05 Jan 2024 12:29:05 -0600, Dave Hansen <dave.hansen@intel.com>
wrote:
> There's very little about how the LRU design came to be in this cover
> letter. Let's add some details.
>
> How's this?
>
> Writing this up, I'm a lot more convinced that this series is, in
> general, taking the right approach. I honestly don't see any other
> alternatives. As much as I'd love to do something stupidly simple like
> just killing enclaves at the moment they hit the limit, that would be a
> horrid experience for users _and_ a departure from what the existing
> reclaim support does.
>
> That said, there's still a lot of work do to do refactor this series.
> It's in need of some love to make it more clear what is going on and to
> making the eventual switch over to per-cgroup LRUs more gradual. Each
> patch in the series is still doing way too much, _especially_ in patch
> 10.
>
> ==
>
> The existing EPC memory management aims to be a miniature version of the
> core VM where EPC memory can be overcommitted and reclaimed. EPC
> allocations can wait for reclaim. The alternative to waiting would have
> been to send a signal and let the enclave die.
>
> This series attempts to implement that same logic for cgroups, for the
> same reasons: it's preferable to wait for memory to become available and
> let reclaim happen than to do things that are fatal to enclaves.
>
> There is currently a global reclaimable page SGX LRU list. That list
> (and the existing scanning algorithm) is essentially useless for doing
> reclaim when a cgroup hits its limit because the cgroup's pages are
> scattered around that LRU. It is unspeakably inefficient to scan a
> linked list with millions of entries for what could be dozens of pages
> from a cgroup that needs reclaim.
>
> Even if unspeakably slow reclaim was accepted, the existing scanning
> algorithm only picks a few pages off the head of the global LRU. It
> would either need to hold the list locks for unreasonable amounts of
> time, or be taught to scan the list in pieces, which has its own
> challenges.
>
> tl;dr: An cgroup hitting its limit should be as similar as possible to
> the system running out of EPC memory. The only two choices to implement
> that are nasty changes the existing LRU scanning algorithm, or to add
> new LRUs. The result: Add a new LRU for each cgroup and scans those
> instead. Replace the existing global cgroup with the root cgroup's LRU
> (only when this new support is compiled in, obviously).
>
I'll add this to the cover letter as a section justifying the LRU design
for per-cgroup reclaiming.
Thank you very much.
Haitao
prev parent reply other threads:[~2024-01-05 20:13 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-30 18:20 [PATCH v6 00/12] Add Cgroup support for SGX EPC memory Haitao Huang
2023-10-30 18:20 ` [PATCH v6 01/12] cgroup/misc: Add per resource callbacks for CSS events Haitao Huang
2023-11-15 20:25 ` Jarkko Sakkinen
2024-01-09 3:37 ` Haitao Huang
2024-01-10 19:55 ` Jarkko Sakkinen
2024-01-05 9:45 ` Michal Koutný
2024-01-06 1:42 ` Haitao Huang
2023-10-30 18:20 ` [PATCH v6 02/12] cgroup/misc: Export APIs for SGX driver Haitao Huang
2023-10-30 18:20 ` [PATCH v6 03/12] cgroup/misc: Add SGX EPC resource type Haitao Huang
2023-10-30 18:20 ` [PATCH v6 04/12] x86/sgx: Implement basic EPC misc cgroup functionality Haitao Huang
2023-11-06 12:09 ` Huang, Kai
2023-11-06 18:59 ` Haitao Huang
2023-11-06 22:18 ` Huang, Kai
2023-11-07 1:16 ` Haitao Huang
2023-11-07 2:08 ` Haitao Huang
2023-11-07 19:07 ` Huang, Kai
2023-11-20 3:16 ` Huang, Kai
2023-11-26 16:01 ` Haitao Huang
2023-11-26 16:32 ` Haitao Huang
2023-11-06 22:23 ` Huang, Kai
2023-11-15 20:48 ` Jarkko Sakkinen
2023-10-30 18:20 ` [PATCH v6 05/12] x86/sgx: Add sgx_epc_lru_list to encapsulate LRU list Haitao Huang
2023-10-30 18:20 ` [PATCH v6 06/12] x86/sgx: Use sgx_epc_lru_list for existing active page list Haitao Huang
2023-10-30 18:20 ` [PATCH v6 07/12] x86/sgx: Introduce EPC page states Haitao Huang
2023-11-15 20:53 ` Jarkko Sakkinen
2024-01-05 17:57 ` Dave Hansen
2024-01-06 1:45 ` Haitao Huang
2023-10-30 18:20 ` [PATCH v6 08/12] x86/sgx: Use a list to track to-be-reclaimed pages Haitao Huang
2023-11-15 20:59 ` Jarkko Sakkinen
2023-10-30 18:20 ` [PATCH v6 09/12] x86/sgx: Restructure top-level EPC reclaim function Haitao Huang
2023-11-20 3:45 ` Huang, Kai
2023-11-26 16:27 ` Haitao Huang
2023-11-27 9:57 ` Huang, Kai
2023-12-12 4:04 ` Haitao Huang
2023-12-13 11:17 ` Huang, Kai
2023-12-15 19:49 ` Haitao Huang
2023-12-18 1:44 ` Huang, Kai
2023-12-18 17:32 ` Mikko Ylinen
2023-12-18 21:24 ` Haitao Huang
2024-01-03 16:37 ` Dave Hansen
2024-01-04 19:11 ` Haitao Huang
2024-01-04 19:19 ` Jarkko Sakkinen
2024-01-04 19:27 ` Dave Hansen
2024-01-04 21:01 ` Haitao Huang
2024-01-05 14:43 ` Mikko Ylinen
2024-01-04 12:38 ` Michal Koutný
2024-01-04 19:20 ` Haitao Huang
2024-01-12 17:07 ` Haitao Huang
2024-01-13 21:04 ` Jarkko Sakkinen
2024-01-13 21:08 ` Jarkko Sakkinen
2023-10-30 18:20 ` [PATCH v6 10/12] x86/sgx: Implement EPC reclamation for cgroup Haitao Huang
2023-11-06 15:58 ` [PATCH] x86/sgx: Charge proper mem_cgroup for usage due to EPC reclamation by cgroups Haitao Huang
2023-11-06 16:10 ` [PATCH v6 10/12] x86/sgx: Implement EPC reclamation for cgroup Haitao Huang
2023-10-30 18:20 ` [PATCH v6 11/12] Docs/x86/sgx: Add description for cgroup support Haitao Huang
2023-10-30 18:20 ` [PATCH v6 12/12] selftests/sgx: Add scripts for EPC cgroup testing Haitao Huang
2023-11-15 21:00 ` Jarkko Sakkinen
2023-11-15 21:22 ` Haitao Huang
2023-11-06 3:26 ` [PATCH v6 00/12] Add Cgroup support for SGX EPC memory Jarkko Sakkinen
2023-11-06 15:48 ` Haitao Huang
2023-11-08 1:00 ` Haitao Huang
2024-01-05 18:29 ` Dave Hansen
2024-01-05 20:13 ` Haitao Huang [this message]
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