Hello Vladimir,

On Tue, Apr 28, 2015 at 03:24:39PM +0300, Vladimir Davydov wrote:

Hi,

This patch set introduces a new user API for tracking user memory pages
that have not been used for a given period of time. The purpose of this
is to provide the userspace with the means of tracking a workload's
working set, i.e. the set of pages that are actively used by the
workload. Knowing the working set size can be useful for partitioning
the system more efficiently, e.g. by tuning memory cgroup limits
appropriately, or for job placement within a compute cluster.

---- USE CASES ----

The unified cgroup hierarchy has memory.low and memory.high knobs, which
are defined as the low and high boundaries for the workload working set
size. However, the working set size of a workload may be unknown or
change in time. With this patch set, one can periodically estimate the
amount of memory unused by each cgroup and tune their memory.low and
memory.high parameters accordingly, therefore optimizing the overall
memory utilization.

Another use case is balancing workloads within a compute cluster.
Knowing how much memory is not really used by a workload unit may help
take a more optimal decision when considering migrating the unit to
another node within the cluster.

---- USER API ----

The user API consists of two new proc files:

 * /proc/kpageidle.  For each page this file contains a 64-bit number, which
   equals 1 if the page is idle or 0 otherwise, indexed by PFN. A page is

Why do we need 64bit per page to indicate just idle or not?
What do you imagine we're happy with other 63bit in future?

-- 
Kind regards,
Minchan Kim

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