On Wed, 13 Jul 2016, Tetsuo Handa wrote:
> I wonder whether commit f9054c70d28bc214 ("mm, mempool: only set
> __GFP_NOMEMALLOC if there are free elements") is doing correct thing.
> It says
>
> If an oom killed thread calls mempool_alloc(), it is possible that it'll
> loop forever if there are no elements on the freelist since
> __GFP_NOMEMALLOC prevents it from accessing needed memory reserves in
> oom conditions.
>
> but we can allow mempool_alloc(__GFP_NOMEMALLOC) requests to access
> memory reserves via below change, can't we? The purpose of allowing
> ALLOC_NO_WATERMARKS via TIF_MEMDIE is to make sure current allocation
> request does not to loop forever inside the page allocator, isn't it?
This would defeat the purpose of __GFP_NOMEMALLOC for oom killed threads,
so you'd need to demonstrate that isn't a problem for the current users
and then change the semantics of the gfp flag.
> Why we need to allow mempool_alloc(__GFP_NOMEMALLOC) requests to use
> ALLOC_NO_WATERMARKS when TIF_MEMDIE is not set?
>
mempool_alloc(__GFP_NOMEMALLOC) is forbidden.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>