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From 1b5e4c317d80f4826eceb3781702d18d06b14394 Mon Sep 17 00:00:00 2001
From: "T.J. Alumbaugh" <talumbau@google.com>
Date: Wed, 18 Jan 2023 00:18:21 +0000
Subject: [PATCH 12/19] UPSTREAM: mm: multi-gen LRU: section for working set
protection
Patch series "mm: multi-gen LRU: improve".
This patch series improves a few MGLRU functions, collects related
functions, and adds additional documentation.
This patch (of 7):
Add a section for working set protection in the code and the design doc.
The admin doc already contains its usage.
Link: https://lkml.kernel.org/r/20230118001827.1040870-1-talumbau@google.com
Link: https://lkml.kernel.org/r/20230118001827.1040870-2-talumbau@google.com
Change-Id: I65599075fd42951db7739a2ab7cee78516e157b3
Signed-off-by: T.J. Alumbaugh <talumbau@google.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
(cherry picked from commit 7b8144e63d84716f16a1b929e0c7e03ae5c4d5c1)
Bug: 274865848
Signed-off-by: T.J. Mercier <tjmercier@google.com>
---
Documentation/mm/multigen_lru.rst | 15 +++++++++++++++
mm/vmscan.c | 4 ++++
2 files changed, 19 insertions(+)
diff --git a/Documentation/mm/multigen_lru.rst b/Documentation/mm/multigen_lru.rst
index d8f721f98868a..6e1483e70fdca 100644
--- a/Documentation/mm/multigen_lru.rst
+++ b/Documentation/mm/multigen_lru.rst
@@ -141,6 +141,21 @@ loop has detected outlying refaults from the tier this page is in. To
this end, the feedback loop uses the first tier as the baseline, for
the reason stated earlier.
+Working set protection
+----------------------
+Each generation is timestamped at birth. If ``lru_gen_min_ttl`` is
+set, an ``lruvec`` is protected from the eviction when its oldest
+generation was born within ``lru_gen_min_ttl`` milliseconds. In other
+words, it prevents the working set of ``lru_gen_min_ttl`` milliseconds
+from getting evicted. The OOM killer is triggered if this working set
+cannot be kept in memory.
+
+This time-based approach has the following advantages:
+
+1. It is easier to configure because it is agnostic to applications
+ and memory sizes.
+2. It is more reliable because it is directly wired to the OOM killer.
+
Summary
-------
The multi-gen LRU can be disassembled into the following parts:
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 596fed6ae0439..ab0b8d3b9d88f 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -4459,6 +4459,10 @@ static bool try_to_inc_max_seq(struct lruvec *lruvec, unsigned long max_seq,
return true;
}
+/******************************************************************************
+ * working set protection
+ ******************************************************************************/
+
static bool lruvec_is_sizable(struct lruvec *lruvec, struct scan_control *sc)
{
int gen, type, zone;
--
2.40.1
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