Re: [PATCH v9 09/15] x86/sgx: Charge mem_cgroup for per-cgroup reclamation

Haitao Huang
2024-02-16T06:07:34Z

Hi Dave,

On Thu, 15 Feb 2024 17:43:18 -0600, Dave Hansen <dave.hansen@intel.com>
wrote:

> On 2/5/24 13:06, Haitao Huang wrote:
>> static struct mem_cgroup *sgx_encl_get_mem_cgroup(struct sgx_encl
>> *encl)
>> {
>> @@ -1003,14 +1001,6 @@ static struct mem_cgroup
>> *sgx_encl_get_mem_cgroup(struct sgx_encl *encl)
>> struct sgx_encl_mm *encl_mm;
>> int idx;
>>
>> - /*
>> - * If called from normal task context, return the mem_cgroup
>> - * of the current task's mm. The remainder of the handling is for
>> - * ksgxd.
>> - */
>> - if (!current_is_ksgxd())
>> - return get_mem_cgroup_from_mm(current->mm);
>
> Why is this being removed?
>
> Searching the enclave mm list is a last resort. It's expensive and
> imprecise.
>
> get_mem_cgroup_from_mm(current->mm), on the other hand is fast and
> precise.
>

I introduced a boolean flag to indicate caller is in kthread (ksgxd or
cgroup workqueue), so sgx_encl_alloc_backing only calls this function if
that flag is true, meaning search through the mm_list is needed.

But now I think a more straightforward way is to just replace
current_is_ksgxd() with (current->flags & PF_KTHREAD).

Thanks

Haitao