From 1b5e4c317d80f4826eceb3781702d18d06b14394 Mon Sep 17 00:00:00 2001 From: "T.J. Alumbaugh" 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 Cc: Yu Zhao Signed-off-by: Andrew Morton (cherry picked from commit 7b8144e63d84716f16a1b929e0c7e03ae5c4d5c1) Bug: 274865848 Signed-off-by: T.J. Mercier --- Documentation/mm/multigen_lru.rst | 15 +++++++++++++++ mm/vmscan.c | 4 ++++ 2 files changed, 19 insertions(+) --- a/Documentation/mm/multigen_lru.rst +++ b/Documentation/mm/multigen_lru.rst @@ -141,6 +141,21 @@ loop has detected outlying refaults from 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: --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -4461,6 +4461,10 @@ done: return true; } +/****************************************************************************** + * working set protection + ******************************************************************************/ + static bool lruvec_is_sizable(struct lruvec *lruvec, struct scan_control *sc) { int gen, type, zone;