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

From: Anshuman Khandual
Date: Thu Oct 13 2016 - 16:10:19 EST

On 09/20/2016 06:24 AM, David Rientjes wrote:
> 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.

Okay. Seems like the general view is that this interface is not necessary.
Hence wont be posting the debugfs version for now.