Re: slab: introduce the flag SLAB_MINIMIZE_WASTE

[Christopher Lameter]

On Mon, 16 Apr 2018, Mikulas Patocka wrote:

> dm-bufio deals gracefully with allocation failure, because it preallocates
> some buffers with vmalloc, but other subsystems may not deal with it and
> they cound return ENOMEM randomly or misbehave in other ways. So, the
> "SLAB_MINIMIZE_WASTE" flag is also saying that the allocation may fail and
> the caller is prepared to deal with it.
>
> The slub subsystem does actual fallback to low-order when the allocation
> fails (it allows different order for each slab in the same cache), but
> slab doesn't fallback and you get NULL if higher-order allocation fails.
> So, SLAB_MINIMIZE_WASTE is needed for slab because it will just randomly
> fail with higher order.

Fix Slab instead of adding a flag that is only useful for one allocator?