On 19.04.19 16:28, Mel Gorman wrote: > On Fri, Apr 19, 2019 at 07:05:21AM -0700, Matthew Wilcox wrote: >> On Fri, Apr 19, 2019 at 10:43:35AM +0100, Mel Gorman wrote: >>> DISCONTIG is essentially deprecated and even parisc plans to move to >>> SPARSEMEM so there is no need to be fancy, this patch simply disables >>> watermark boosting by default on DISCONTIGMEM. >> >> I don't think parisc is the only arch which uses DISCONTIGMEM for !NUMA >> scenarios. Grepping the arch/ directories shows: >> >> alpha (does support NUMA, but also non-NUMA DISCONTIGMEM) >> arc (for supporting more than 1GB of memory) >> ia64 (looks complicated ...) >> m68k (for multiple chunks of memory) >> mips (does support NUMA but also non-NUMA) >> parisc (both NUMA and non-NUMA) >> >> I'm not sure that these architecture maintainers even know that DISCONTIGMEM >> is deprecated. Adding linux-arch to the cc. > > Poor wording then -- yes, DISCONTIGMEM is still used but look where it's > used. I find it impossible to believe that any new arch would support > DISCONTIGMEM or that DISCONTIGMEM would be selected when SPARSEMEM is > available.`It's even more insane when you consider that SPARSEMEM can be > extended to support VMEMMAP so that it has similar overhead to FLATMEM > when mapping pfns to struct pages and vice-versa. FYI, on parisc we will switch from DISCONTIGMEM to SPARSEMEM with kernel 5.2. The patch was quite simple and it's currently in the for-next tree: https://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux.git/commit/?h=for-next&id=281b718721a5e78288271d632731cea9697749f7 Helge
