On Tue, Jan 26, 2016 at 5:18 PM, Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> wrote: > Hello, > > On Tue, Jan 26, 2016 at 03:11:36PM -0800, Dan Williams wrote: >> On Tue, Jan 26, 2016 at 2:51 PM, Andrew Morton >> <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: >> > On Tue, 26 Jan 2016 14:33:48 -0800 Dan Williams <dan.j.williams@xxxxxxxxx> wrote: >> > >> >> >> Towards this end, alias ZONE_DMA and ZONE_DEVICE to work around needing >> >> >> to maintain a unique zone number for ZONE_DEVICE. Record the geometry >> >> >> of ZONE_DMA at init (->init_spanned_pages) and use that information in >> >> >> is_zone_device_page() to differentiate pages allocated via >> >> >> devm_memremap_pages() vs true ZONE_DMA pages. Otherwise, use the >> >> >> simpler definition of is_zone_device_page() when ZONE_DMA is turned off. >> >> >> >> >> >> Note that this also teaches the memory hot remove path that the zone may >> >> >> not have sections for all pfn spans (->zone_dyn_start_pfn). >> >> >> >> >> >> A user visible implication of this change is potentially an unexpectedly >> >> >> high "spanned" value in /proc/zoneinfo for the DMA zone. >> >> > >> >> > Well, all these icky tricks are to avoid increasing ZONES_SHIFT, yes? >> >> > Is it possible to just use ZONES_SHIFT=3? >> >> >> >> Last I tried I hit this warning in mm/memory.c >> >> >> >> #warning Unfortunate NUMA and NUMA Balancing config, growing >> >> page-frame for last_cpupid. >> > >> > Well yes, it may take a bit of work - perhaps salvaging a bit from >> > somewhere else if poss. But that might provide a better overall >> > solution so could you please have a think? >> > >> >> Will do, especially since other efforts are feeling the pinch on the >> MAX_NR_ZONES limitation. > > Please refer my previous attempt to add a new zone, ZONE_CMA. > > https://lkml.org/lkml/2015/2/12/84 > > It salvages a bit from SECTION_WIDTH by increasing section size. > Similarly, I guess we can reduce NODE_WIDTH if needed although > it could cause to reduce maximum node size. Dave pointed out to me that LAST__PID_SHIFT might be a better candidate to reduce to 7 bits. That field is for storing pids which are already bigger than 8 bits. If it is relying on the fact that pids don't rollover very often then likely the impact of 7-bits instead of 8 will be minimal. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>