On Tue, Jan 26, 2016 at 05:37:38PM -0800, Dan Williams wrote: > 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. Hmm... I'm not sure it's possible or not, but, it looks not a general solution. It will solve your problem because you are using 64 bit arch but other 32 bit archs can't get the benefit. Thanks. -- 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>