Comment # 3 on bug 1224805 from Vlastimil Babka

+CC Juergen

order-4 and higher are considered "costly" and might give up trying to free and
defragment (compact) memory sooner than later. The __GFP_RETRY_MAYFAIL flag can
be used to try harder.

But I wonder why privcmd_buf_mmap() really needs such a large allocation? I can
only see:

vma_priv = kzalloc(struct_size(vma_priv, pages, count), GFP_KERNEL);

and for that to get large, we would need many pages. If I count correctly, it's
at least 4096 page pointers to get us over order-3 into order-4. Hm so it's
maybe just a 16MB+ VMA and that can be expected here? In that case I'd
recommend kvzalloc() instead of kvmalloc().