On 9/10/19 1:40 PM, Dan Williams wrote:
On Mon, Sep 9, 2019 at 11:29 PM Aneesh Kumar K.V
<aneesh.ku...@linux.ibm.com> wrote:
With PFN_MODE_PMEM namespace, the memmap area is allocated from the device
area. Some architectures map the memmap area with large page size. On
architectures like ppc64, 16MB page for memap mapping can map 262144 pfns.
This maps a namespace size of 16G.
When populating memmap region with 16MB page from the device area,
make sure the allocated space is not used to map resources outside this
namespace. Such usage of device area will prevent a namespace destroy.
Add resource end pnf in altmap and use that to check if the memmap area
allocation can map pfn outside the namespace. On ppc64 in such case we fallback
to allocation from memory.
Shouldn't this instead be comprehended by nd_pfn_init() to increase
the reservation size so that it fits in the alignment? It may not
always be possible to fall back to allocation from memory for
extremely large pmem devices. I.e. at 64GB of memmap per 1TB of pmem
there may not be enough DRAM to store the memmap.
We do switch between DRAM and device for memmap allocation. ppc64
vmemmap_populate does
if (altmap && !altmap_cross_boundary(altmap, start, page_size)) {
p = altmap_alloc_block_buf(page_size, altmap);
if (!p)
pr_debug("altmap block allocation failed, falling back to system
memory");
}
if (!p)
p = vmemmap_alloc_block_buf(page_size, node);
With that we should be using DRAM for the first and the last mapping,
rest of the memmap should be backed by device.
-aneesh
