On Tue, 17 Apr 2018, Christopher Lameter wrote: > 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? Slab assumes that all slabs have the same order, so it's not so easy to fix it. Mikulas
