Re: [PATCH V4] mm: Add sysfs interface to dump each node's zonelist information

[David Rientjes]

On Sat, 17 Sep 2016, Anshuman Khandual wrote:

> > I'm questioning if this information can be inferred from information 
> > already in /proc/zoneinfo and sysfs.  We know the no-fallback zonelist is 
> > going to include the local node, and we know the other zonelists are 
> > either node ordered or zone ordered (or do we need to extend 
> > vm.numa_zonelist_order for default?).  I may have missed what new 
> > knowledge this interface is imparting on us.
> 
> IIUC /proc/zoneinfo lists down zone internal state and statistics for
> all zones on the system at any given point of time. The no-fallback
> list contains the zones from the local node and fallback (which gets
> used more often than the no-fallback) list contains all zones either
> in node-ordered or zone-ordered manner. In most of the platforms the
> default being the node order but the sequence of present nodes in
> that order is determined by various factors like NUMA distance, load,
> presence of CPUs on the node etc. This order of nodes in the fallback
> list is the most important information derived out of this interface.
> 

The point is that all of this can be inferred with information already 
provided, so the additional interface seems unnecessary.  The only 
extension I think that is needed is to determine if the order is node or 
zone when vm.numa_zonelist_order == default and we shouldn't parse this 
from dmesg.