Re: [RFC 2/3] mm/vmalloc: add support for __GFP_NOFAIL

[Michal Hocko]

On Fri 22-10-21 09:49:08, Neil Brown wrote:
[...]
> However now that I've thought about some more, I'd much prefer we
> introduce something like
>     memalloc_retry_wait();
> 
> and use that everywhere that a memory allocation is retried.
> I'm not convinced that we need to wait at all - at least, not when
> __GFP_DIRECT_RECLAIM is used, as in that case alloc_page will either
>   - succeed
>   - make some progress a reclaiming or
>   - sleep

There
are two that we have to do explicitly vmap_pages_range one is due to
implicit GFP_KERNEL allocations for page tables. Those would likely be a
good fit for something you suggest above. Then we have __get_vm_area_node
retry loop which can be either due to vmalloc space reservation failure
or an implicit GFP_KERNEL allocation by kasan. The first one is not
really related to the memory availability so it doesn't sound like a
good fit.

-- 
Michal Hocko
SUSE Labs