linux-kernel - [PATCH v4 1/2] lib: stackdepot: Add support to configure STACK_HASH

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Date:   Wed, 30 Dec 2020 18:15:30 +0530
From:   vjitta@...eaurora.org
To:     minchan@...nel.org, glider@...gle.com, dan.j.williams@...el.com,
        broonie@...nel.org, mhiramat@...nel.org
Cc:     linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
        vjitta@...eaurora.org, ylal@...eaurora.org, vinmenon@...eaurora.org
Subject: [PATCH v4 1/2] lib: stackdepot: Add support to configure STACK_HASH_SIZE

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

Use STACK_HASH_ORDER_SHIFT 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, default value of
STACK_HASH_SIZE lead stack depot to consume 8MB of static memory.
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>
---
 lib/Kconfig      | 9 +++++++++
 lib/stackdepot.c | 3 +--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/lib/Kconfig b/lib/Kconfig
index 3321d04..fd967fb 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -623,6 +623,15 @@ config STACKDEPOT
 	bool
 	select STACKTRACE
 
+config STACK_HASH_ORDER_SHIFT
+	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 81c69c0..614ac28 100644
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -141,8 +141,7 @@ 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_SHIFT)
 #define STACK_HASH_MASK (STACK_HASH_SIZE - 1)
 #define STACK_HASH_SEED 0x9747b28c
 
-- 
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2.7.4