On Thu, 2022-05-19 at 14:22 -0700, Shakeel Butt wrote: > On Thu, May 19, 2022 at 2:05 PM Kristen Carlson Accardi > <kristen@xxxxxxxxxxxxxxx> wrote: > > When the system runs out of enclave memory, SGX can reclaim EPC > > pages > > by swapping to normal RAM. These backing pages are allocated via a > > per-enclave shared memory area. Since SGX allows unlimited over > > commit on EPC memory, the reclaimer thread can allocate a large > > number of backing RAM pages in response to EPC memory pressure. > > > > When the shared memory backing RAM allocation occurs during > > the reclaimer thread context, the shared memory is charged to > > the root memory control group, and the shmem usage of the enclave > > is not properly accounted for, making cgroups ineffective at > > limiting the amount of RAM an enclave can consume. > > > > For example, when using a cgroup to launch a set of test > > enclaves, the kernel does not properly account for 50% - 75% of > > shmem page allocations on average. In the worst case, when > > nearly all allocations occur during the reclaimer thread, the > > kernel accounts less than a percent of the amount of shmem used > > by the enclave's cgroup to the correct cgroup. > > > > SGX stores a list of mm_structs that are associated with > > an enclave. Pick one of them during reclaim and charge that > > mm's memcg with the shmem allocation. The one that gets picked > > is arbitrary, but this list almost always only has one mm. The > > cases where there is more than one mm with different memcg's > > are not worth considering. > > > > Create a new function - sgx_encl_alloc_backing(). This function > > is used whenever a new backing storage page needs to be > > allocated. Previously the same function was used for page > > allocation as well as retrieving a previously allocated page. > > Prior to backing page allocation, if there is a mm_struct > > associated > > with the enclave that is requesting the allocation, it is set > > as the active memory control group. > > > > Signed-off-by: Kristen Carlson Accardi <kristen@xxxxxxxxxxxxxxx> > > For the memcg part: > > Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx> Thanks!
