Date:   Tue,  4 Jan 2022 13:22:28 -0700
In-Reply-To: <20220104202227.2903605-1-yuzhao@google.com>
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Subject: [PATCH v6 9/9] mm: multigenerational lru: Kconfig
From:   Yu Zhao <yuzhao@google.com>
To:     Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Andi Kleen <ak@linux.intel.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Hillf Danton <hdanton@sina.com>, Jens Axboe <axboe@kernel.dk>,
        Jesse Barnes <jsbarnes@google.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Jonathan Corbet <corbet@lwn.net>,
        Matthew Wilcox <willy@infradead.org>,
        Mel Gorman <mgorman@suse.de>,
        Michael Larabel <Michael@michaellarabel.com>,
        Michal Hocko <mhocko@kernel.org>,
        Rik van Riel <riel@surriel.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Will Deacon <will@kernel.org>,
        Ying Huang <ying.huang@intel.com>,
        linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        page-reclaim@google.com, x86@kernel.org,
        Yu Zhao <yuzhao@google.com>,
        Konstantin Kharlamov <Hi-Angel@yandex.ru>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Add configuration options for the multigenerational lru.

Signed-off-by: Yu Zhao <yuzhao@google.com>
Tested-by: Konstantin Kharlamov <Hi-Angel@yandex.ru>
---
 Documentation/vm/multigen_lru.rst | 18 ++++++++++++
 mm/Kconfig                        | 48 +++++++++++++++++++++++++++++++
 2 files changed, 66 insertions(+)

diff --git a/Documentation/vm/multigen_lru.rst b/Documentation/vm/multigen_lru.rst
index 6f9e0181348b..a54c5637c455 100644
--- a/Documentation/vm/multigen_lru.rst
+++ b/Documentation/vm/multigen_lru.rst
@@ -6,6 +6,13 @@ Multigenerational LRU
 
 Quick start
 ===========
+Build configurations
+--------------------
+:Required: Set ``CONFIG_LRU_GEN=y``.
+
+:Optional: Set ``CONFIG_LRU_GEN_ENABLED=y`` to enable this feature by
+ default.
+
 Runtime configurations
 ----------------------
 :Required: Write ``1`` to ``/sys/kernel/mm/lru_gen/enable`` if the
@@ -25,6 +32,17 @@ Personal computers
 
 Data centers
 ------------
+:Optional: Change ``CONFIG_NR_LRU_GENS`` to a larger value to support
+ more generations for ``Working set estimation`` and
+ ``Proactive reclaim``.
+
+:Optional: Change ``CONFIG_TIERS_PER_GEN`` to a larger value to
+ support more tiers, which generally provide better protection for
+ page cache when under heavy buffered I/O workloads.
+
+:Optional: Set ``CONFIG_LRU_GEN_STATS=y`` to enable full stats for
+ debugging. See ``Debugfs interface``.
+
 :Debugfs interface: ``/sys/kernel/debug/lru_gen`` has the following
  format:
  ::
diff --git a/mm/Kconfig b/mm/Kconfig
index 356f4f2c779e..8a33605917f5 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -900,6 +900,54 @@ config IO_MAPPING
 config SECRETMEM
 	def_bool ARCH_HAS_SET_DIRECT_MAP && !EMBEDDED
 
+# multigenerational lru {
+config LRU_GEN
+	bool "Multigenerational LRU"
+	depends on MMU
+	# the following options can use up the spare bits in page flags
+	depends on !MAXSMP && (64BIT || !SPARSEMEM || SPARSEMEM_VMEMMAP)
+	help
+	  A high performance LRU implementation for memory overcommit. See
+	  Documentation/vm/multigen_lru.rst for details.
+
+config LRU_GEN_ENABLED
+	bool "Enable by default"
+	depends on LRU_GEN
+	help
+	  This option enables the multigenerational lru by default.
+
+config NR_LRU_GENS
+	int "Max number of generations"
+	depends on LRU_GEN
+	range 4 31
+	default 4
+	help
+	  This option uses order_base_2(N+1) bits in page flags.
+
+	  Do not configure more generations than you plan to use. They have a
+	  per-memcg and per-node memory overhead.
+
+config TIERS_PER_GEN
+	int "Number of tiers per generation"
+	depends on LRU_GEN
+	range 2 5
+	default 4
+	help
+	  This option uses N-2 bits in page flags.
+
+	  Larger values generally provide better protection for page cache when
+	  under heavy buffered I/O workloads.
+
+config LRU_GEN_STATS
+	bool "Full stats for debugging"
+	depends on LRU_GEN
+	help
+	  This option keeps historical stats for evicted generations.
+
+	  Do not enable full stats unless you plan to look at them. They have a
+	  per-memcg and per-node memory overhead.
+# }
+
 source "mm/damon/Kconfig"
 
 endmenu
-- 
2.34.1.448.ga2b2bfdf31-goog