Messages in this thread | | | Subject | Re: [PATCH v2 1/2] x86/sgx: Add accounting for tracking overcommit | Date | Tue, 11 Jan 2022 08:20:32 -0600 | From | "Haitao Huang" <> |
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On Fri, 07 Jan 2022 13:16:12 -0600, Kristen Carlson Accardi <kristen@linux.intel.com> wrote:
> On Fri, 2022-01-07 at 10:46 -0800, Dave Hansen wrote: >> On 1/7/22 10:16, Kristen Carlson Accardi wrote: >> > The overcommit percentage value is 150, which limits the total >> > number of >> > shared memory pages that may be consumed by all enclaves as backing >> > pages >> > to 1.5X of EPC pages on the system. >> >> Hi Kristen, >> >> Could you give some background on how this value was chosen and how >> it >> might impact userspace? > > Yes, > The value of 1.5x the number of EPC pages was chosen because it will > handle the most common case of a few enclaves that don't need much > overcommit without any impact to user space. In the less commone case > where there are many enclaves or a few large enclaves which need a lot > of overcommit due to large EPC memory requirements, the reclaimer may > fail to allocate a backing page for swapping if the limit has been > reached. In this case the page will not be able to be reclaimed and the > system will not be able to allocate any new EPC pages. Any ioctl or > call to add new EPC pages will get -ENOMEM, so for example, new > enclaves will fail to load, and new EPC pages will not be able to be > added. > > Does that make sense?
If the system has a ton of RAM but limited EPC, I think it makes sense to allow more EPC swapping, can we do min(0.5*RAM, 2*EPC)? I suppose if the system is used for heavy enclave load, user would be willing to at least use half of RAM.
Thanks Haitao
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