linux-imx/sysfs-kernel-mm-numa at lf-6.6.y

mirror of https://github.com/nxp-imx/linux-imx.git synced 2025-09-03 02:16:09 +02:00

Huang Ying 20b51af15e mm/migrate: add sysfs interface to enable reclaim migration

Some method is obviously needed to enable reclaim-based migration.

Just like traditional autonuma, there will be some workloads that will
benefit like workloads with more "static" configurations where hot pages
stay hot and cold pages stay cold.  If pages come and go from the hot and
cold sets, the benefits of this approach will be more limited.

The benefits are truly workload-based and *not* hardware-based.  We do not
believe that there is a viable threshold where certain hardware
configurations should have this mechanism enabled while others do not.

To be conservative, earlier work defaulted to disable reclaim- based
migration and did not include a mechanism to enable it.  This proposes add
a new sysfs file

  /sys/kernel/mm/numa/demotion_enabled

as a method to enable it.

We are open to any alternative that allows end users to enable this
mechanism or disable it if workload harm is detected (just like
traditional autonuma).

Once this is enabled page demotion may move data to a NUMA node that does
not fall into the cpuset of the allocating process.  This could be
construed to violate the guarantees of cpusets.  However, since this is an
opt-in mechanism, the assumption is that anyone enabling it is content to
relax the guarantees.

Link: https://lkml.kernel.org/r/20210721063926.3024591-9-ying.huang@intel.com
Link: https://lkml.kernel.org/r/20210715055145.195411-10-ying.huang@intel.com
Signed-off-by: Huang Ying <ying.huang@intel.com>
Originally-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Wei Xu <weixugc@google.com>
Cc: Yang Shi <yang.shi@linux.alibaba.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Keith Busch <kbusch@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2021-09-03 09:58:16 -07:00

1.0 KiB

Raw Permalink Blame History

What: /sys/kernel/mm/numa/ Date: June 2021 Contact: Linux memory management mailing list linux-mm@kvack.org Description: Interface for NUMA

What: /sys/kernel/mm/numa/demotion_enabled Date: June 2021 Contact: Linux memory management mailing list linux-mm@kvack.org Description: Enable/disable demoting pages during reclaim

	Page migration during reclaim is intended for systems
	with tiered memory configurations.  These systems have
	multiple types of memory with varied performance
	characteristics instead of plain NUMA systems where
	the same kind of memory is found at varied distances.
	Allowing page migration during reclaim enables these
	systems to migrate pages from fast tiers to slow tiers
	when the fast tier is under pressure.  This migration
	is performed before swap.  It may move data to a NUMA
	node that does not fall into the cpuset of the
	allocating process which might be construed to violate
	the guarantees of cpusets.  This should not be enabled
	on systems which need strict cpuset location
	guarantees.

1.0 KiB Raw Permalink Blame History

1.0 KiB

Raw Permalink Blame History