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From: Dave Hansen <dave.hansen@linux.intel.com>
To: linux-kernel@vger.kernel.org
Cc: Dave Hansen <dave.hansen@linux.intel.com>,
	yang.shi@linux.alibaba.com, rientjes@google.com,
	ying.huang@intel.com, dan.j.williams@intel.com
Subject: [RFC][PATCH 04/12] mm/numa: node demotion data structure and lookup
Date: Tue, 06 Oct 2020 13:51:12 -0700	[thread overview]
Message-ID: <20201006205112.5746B090@viggo.jf.intel.com> (raw)
In-Reply-To: <20201006205103.268F74A9@viggo.jf.intel.com>


From: Dave Hansen <dave.hansen@linux.intel.com>

Prepare for the kernel to auto-migrate pages to other memory nodes
with a user defined node migration table. This allows creating single
migration target for each NUMA node to enable the kernel to do NUMA
page migrations instead of simply reclaiming colder pages. A node
with no target is a "terminal node", so reclaim acts normally there.
The migration target does not fundamentally _need_ to be a single node,
but this implementation starts there to limit complexity.

If you consider the migration path as a graph, cycles (loops) in the
graph are disallowed.  This avoids wasting resources by constantly
migrating (A->B, B->A, A->B ...).  The expectation is that cycles will
never be allowed.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Yang Shi <yang.shi@linux.alibaba.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>

--

changes in July 2020:
 - Remove loop from next_demotion_node() and get_online_mems().
   This means that the node returned by next_demotion_node()
   might now be offline, but the worst case is that the
   allocation fails.  That's fine since it is transient.
---

 b/mm/migrate.c |   16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff -puN mm/migrate.c~0006-node-Define-and-export-memory-migration-path mm/migrate.c
--- a/mm/migrate.c~0006-node-Define-and-export-memory-migration-path	2020-10-06 13:39:24.067818434 -0700
+++ b/mm/migrate.c	2020-10-06 13:39:24.071818434 -0700
@@ -1161,6 +1161,22 @@ out:
 	return rc;
 }
 
+static int node_demotion[MAX_NUMNODES] = {[0 ...  MAX_NUMNODES - 1] = NUMA_NO_NODE};
+
+/**
+ * next_demotion_node() - Get the next node in the demotion path
+ * @node: The starting node to lookup the next node
+ *
+ * @returns: node id for next memory node in the demotion path hierarchy
+ * from @node; NUMA_NO_NODE if @node is terminal.  This does not keep
+ * @node online or guarantee that it *continues* to be the next demotion
+ * target.
+ */
+int next_demotion_node(int node)
+{
+	return node_demotion[node];
+}
+
 /*
  * Obtain the lock on page, remove all ptes and migrate the page
  * to the newly allocated page in newpage.
_

  parent reply	other threads:[~2020-10-06 20:51 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-06 20:51 [RFC][PATCH 00/12] mm: tweak page cache migration Dave Hansen
2020-10-06 20:51 ` [RFC][PATCH 01/12] mm/vmscan: restore zone_reclaim_mode ABI Dave Hansen
2020-10-07  8:45   ` Christopher Lameter
2020-10-06 20:51 ` [RFC][PATCH 02/12] mm/vmscan: move RECLAIM* bits to uapi header Dave Hansen
2020-10-07  8:45   ` Christopher Lameter
2020-10-06 20:51 ` [RFC][PATCH 03/12] mm/vmscan: replace implicit RECLAIM_ZONE checks with explicit checks Dave Hansen
2020-10-07  8:47   ` Christopher Lameter
2020-10-06 20:51 ` Dave Hansen [this message]
2020-10-06 20:51 ` [RFC][PATCH 05/12] mm/numa: automatically generate node migration order Dave Hansen
2020-10-06 20:51 ` [RFC][PATCH 06/12] mm/migrate: update migration order during on hotplug events Dave Hansen
2020-10-06 20:51 ` [RFC][PATCH 07/12] mm/migrate: make migrate_pages() return nr_succeeded Dave Hansen
2020-10-06 20:51 ` [RFC][PATCH 08/12] mm/migrate: demote pages during reclaim Dave Hansen
2020-10-06 20:51 ` [RFC][PATCH 09/12] mm/vmscan: add page demotion counter Dave Hansen
2020-10-06 20:51 ` [RFC][PATCH 10/12] mm/vmscan: Consider anonymous pages without swap Dave Hansen
2020-10-06 20:51 ` [RFC][PATCH 11/12] mm/vmscan: never demote for memcg reclaim Dave Hansen
2020-10-06 20:51 ` [RFC][PATCH 12/12] mm/migrate: new zone_reclaim_mode to enable reclaim migration Dave Hansen
2020-10-06 20:53 ` [RFC][PATCH 00/12] mm: tweak page cache migration Dave Hansen
2020-10-07  9:52 ` Michal Hocko
2020-10-07  9:55   ` David Hildenbrand
2020-10-07 15:52     ` Yang Shi
2020-10-07 15:58       ` Dave Hansen

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