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

[Haitao Huang]

Hi Dave,

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