[PATCH v3 5/5] mm/slub: do not create dma-kmalloc if no managed pages in DMA zone

[Christoph Lameter]

On Tue, 14 Dec 2021, Vlastimil Babka wrote:

> If doesn't feel right to me to fix (or rather workaround) this on the level
> of kmalloc caches just because the current reports come from there. If we
> decide it's acceptable for kdump kernel to return !ZONE_DMA memory for
> GFP_DMA requests, then it should apply at the page allocator level for all
> allocations, not just kmalloc().
>
> Also you mention above you'd prefer ZONE_DMA32 memory, while chances are
> this approach of using KMALLOC_NORMAL caches will end up giving you
> ZONE_NORMAL. On the page allocator level it would be much easier to
> implement a fallback from non-populated ZONE_DMA to ZONE_DMA32 specifically.

Well this only works if the restrictions on the physical memory addresses
of each platform make that possible.