Thx Michal,
On Tue, Jan 08, 2019 at 04:40:31PM +0100, Michal Hocko wrote:
> On Tue 08-01-19 17:51:07, Guo Ren wrote:
> [...]
> > static inline pte_t *pte_alloc_one_kernel(struct mm_struct *mm)
> > {
> > pte_t *pte;
> > unsigned long i;
> >
> > pte = (pte_t *) __get_free_page(GFP_KERNEL | __GFP_RETRY_MAYFAIL);
> > ^^^^^^^^^^^^^^^^^^^
> > It's necessary ?
> > x86 & arm don't use
> > it.
> > if (!pte)
> > return NULL;
>
> That depends on whether you want OOM killer to be triggered for these
> allocations. If you add the flag then the allocation bails out with a
> failure rather than kill an oom victim.
Yes, in page_alloc.c:
if (gfp_mask & __GFP_RETRY_MAYFAIL)
goto out;
...
if (out_of_memory(&oc) || WARN_ON_ONCE(gfp_mask & __GFP_NOFAIL)) {
^^^^^^^^^^^^^ OOM kill victim
...
if (gfp_mask & __GFP_NOFAIL)
page = __alloc_pages_cpuset_fallback(gfp_mask, order,
ALLOC_NO_WATERMARKS, ac);
}
Seems it could affect the behavior of the system which is out of memory.
OOM killer could help to get_page for current. So keep the same as x86 &
arm here. I'll remove __GFP_RETRY_MAYFAIL in patch.
Best Regards
Guo Ren
