linux-kernel - [PATCH v6 1/2] lib: stackdepot: Add support to configure STACK_HASH

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Date:   Wed, 27 Jan 2021 17:36:37 +0530
From:   vjitta@...eaurora.org
To:     minchan@...nel.org, glider@...gle.com, akpm@...ux-foundation.org,
        dan.j.williams@...el.com, broonie@...nel.org, mhiramat@...nel.org
Cc:     linux-kernel@...r.kernel.org, vjitta@...eaurora.org,
        ylal@...eaurora.org, vinmenon@...eaurora.org
Subject: [PATCH v6 1/2] lib: stackdepot: Add support to configure STACK_HASH_SIZE

From: Yogesh Lal <ylal@...eaurora.org>

Use CONFIG_STACK_HASH_ORDER to configure STACK_HASH_SIZE.

Aim is to have configurable value for  STACK_HASH_SIZE,
so depend on use case one can configure it.

One example is of Page Owner, CONFIG_PAGE_OWNER works only
if page_owner=on via kernel parameter on CONFIG_PAGE_OWNER
configured system. Thus, unless admin enable it via command
line option, the stackdepot will just waste 8M memory without
any customer.

Making it configurable and use lower value helps to enable
features like CONFIG_PAGE_OWNER without any significant overhead.

Signed-off-by: Yogesh Lal <ylal@...eaurora.org>
Signed-off-by: Vinayak Menon <vinmenon@...eaurora.org>
Signed-off-by: Vijayanand Jitta <vjitta@...eaurora.org>
Reviewed-by: Minchan Kim <minchan@...nel.org>
Reviewed-by: Alexander Potapenko <glider@...gle.com>
---
 lib/Kconfig      | 9 +++++++++
 lib/stackdepot.c | 3 +--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/lib/Kconfig b/lib/Kconfig
index b46a9fd..96ee125 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -651,6 +651,15 @@ config STACKDEPOT
 	bool
 	select STACKTRACE
 
+config STACK_HASH_ORDER
+	int "stack depot hash size (12 => 4KB, 20 => 1024KB)"
+	range 12 20
+	default 20
+	depends on STACKDEPOT
+	help
+	 Select the hash size as a power of 2 for the stackdepot hash table.
+	 Choose a lower value to reduce the memory impact.
+
 config SBITMAP
 	bool
 
diff --git a/lib/stackdepot.c b/lib/stackdepot.c
index 2caffc6..dff8521 100644
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -142,8 +142,7 @@ static struct stack_record *depot_alloc_stack(unsigned long *entries, int size,
 	return stack;
 }
 
-#define STACK_HASH_ORDER 20
-#define STACK_HASH_SIZE (1L << STACK_HASH_ORDER)
+#define STACK_HASH_SIZE (1L << CONFIG_STACK_HASH_ORDER)
 #define STACK_HASH_MASK (STACK_HASH_SIZE - 1)
 #define STACK_HASH_SEED 0x9747b28c
 
-- 
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