target/linux/generic/backport-6.1/020-v6.3-12-UPSTREAM-mm-multi-gen-LRU-section-for-working-set-pr.patch

   1 From 1b5e4c317d80f4826eceb3781702d18d06b14394 Mon Sep 17 00:00:00 2001
   2 From: "T.J. Alumbaugh" <talumbau@google.com>
   3 Date: Wed, 18 Jan 2023 00:18:21 +0000
   4 Subject: [PATCH 12/19] UPSTREAM: mm: multi-gen LRU: section for working set
   5  protection
   6
   7 Patch series "mm: multi-gen LRU: improve".
   8
   9 This patch series improves a few MGLRU functions, collects related
  10 functions, and adds additional documentation.
  11
  12 This patch (of 7):
  13
  14 Add a section for working set protection in the code and the design doc.
  15 The admin doc already contains its usage.
  16
  17 Link: https://lkml.kernel.org/r/20230118001827.1040870-1-talumbau@google.com
  18 Link: https://lkml.kernel.org/r/20230118001827.1040870-2-talumbau@google.com
  19 Change-Id: I65599075fd42951db7739a2ab7cee78516e157b3
  20 Signed-off-by: T.J. Alumbaugh <talumbau@google.com>
  21 Cc: Yu Zhao <yuzhao@google.com>
  22 Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
  23 (cherry picked from commit 7b8144e63d84716f16a1b929e0c7e03ae5c4d5c1)
  24 Bug: 274865848
  25 Signed-off-by: T.J. Mercier <tjmercier@google.com>
  26 ---
  27  Documentation/mm/multigen_lru.rst | 15 +++++++++++++++
  28  mm/vmscan.c                       |  4 ++++
  29  2 files changed, 19 insertions(+)
  30
  31 --- a/Documentation/mm/multigen_lru.rst
  32 +++ b/Documentation/mm/multigen_lru.rst
  33 @@ -141,6 +141,21 @@ loop has detected outlying refaults from
  34  this end, the feedback loop uses the first tier as the baseline, for
  35  the reason stated earlier.
  36
  37 +Working set protection
  38 +----------------------
  39 +Each generation is timestamped at birth. If ``lru_gen_min_ttl`` is
  40 +set, an ``lruvec`` is protected from the eviction when its oldest
  41 +generation was born within ``lru_gen_min_ttl`` milliseconds. In other
  42 +words, it prevents the working set of ``lru_gen_min_ttl`` milliseconds
  43 +from getting evicted. The OOM killer is triggered if this working set
  44 +cannot be kept in memory.
  45 +
  46 +This time-based approach has the following advantages:
  47 +
  48 +1. It is easier to configure because it is agnostic to applications
  49 +   and memory sizes.
  50 +2. It is more reliable because it is directly wired to the OOM killer.
  51 +
  52  Summary
  53  -------
  54  The multi-gen LRU can be disassembled into the following parts:
  55 --- a/mm/vmscan.c
  56 +++ b/mm/vmscan.c
  57 @@ -4461,6 +4461,10 @@ done:
  58         return true;
  59  }
  60
  61 +/******************************************************************************
  62 + *                          working set protection
  63 + ******************************************************************************/
  64 +
  65  static bool lruvec_is_sizable(struct lruvec *lruvec, struct scan_control *sc)
  66  {
  67         int gen, type, zone;