Re: [dm-devel] [RFC PATCH 2/2] mm, mempool: do not throttle PF_LESS_THROTTLE tasks

[Michal Hocko]

On Thu 24-11-16 12:10:08, Mikulas Patocka wrote:
> 
> 
> On Thu, 24 Nov 2016, Michal Hocko wrote:
[...]
> > Please note that even
> > GFP_NOWAIT allocations will wake up kspwad which should clean up that
> 
> The mempool is also using GFP_NOIO allocations - so do you claim that it 
> should not use GFP_NOIO too?

No, I am not claiming that. The last time I have asked the throttling
didn't seem to serious enough to cause any problems. If the memory
reclaim throttling is serious enough then let's measure and evaluate it.

> You should provide a clear API that the block device drivers should use to 
> allocate memory - not to apply band aid to vm throttling problems as they 
> are being discovered.

This is easier said than done, I am afraid. We have been using GFP_NOIO
in mempool for years and there were no major complains.
-- 
Michal Hocko
SUSE Labs