[PATCH v6 1/2] lib: stackdepot: Add support to configure STACK_HASH_SIZE

[PATCH v6 1/2] lib: stackdepot: Add support to configure STACK_HASH_SIZE

[vjitta]

From: Yogesh Lal <ylal@codeaurora.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@codeaurora.org>
Signed-off-by: Vinayak Menon <vinmenon@codeaurora.org>
Signed-off-by: Vijayanand Jitta <vjitta@codeaurora.org>
Reviewed-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Alexander Potapenko <glider@google.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
 
-- 
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation
2.7.4

[PATCH v6 2/2] lib: stackdepot: Add support to disable stack depot

[vjitta]

From: Vijayanand Jitta <vjitta@codeaurora.org>

Add a kernel parameter stack_depot_disable to disable
stack depot. So that stack hash table doesn't consume
any memory when stack depot is disabled.

The usecase is CONFIG_PAGE_OWNER without page_owner=on.
Without this patch, stackdepot will consume the memory
for the hashtable. By default, it's 8M which is never trivial.

With this option, in CONFIG_PAGE_OWNER configured system,
page_owner=off, stack_depot_disable in kernel command line,
we could save the wasted memory for the hashtable.

Signed-off-by: Vinayak Menon <vinmenon@codeaurora.org>
Signed-off-by: Vijayanand Jitta <vjitta@codeaurora.org>
---
 Documentation/admin-guide/kernel-parameters.txt |  6 +++++
 include/linux/stackdepot.h                      |  1 +
 init/main.c                                     |  2 ++
 lib/stackdepot.c                                | 32 +++++++++++++++++++++----
 4 files changed, 37 insertions(+), 4 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 44fde25..381fad9 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -5133,6 +5133,12 @@
 			growing up) the main stack are reserved for no other
 			mapping. Default value is 256 pages.
 
+	stack_depot_disable= [KNL]
+			Setting this to true through kernel command line will
+			disable the stack depot thereby saving the static memory
+			consumed by the stack hash table. By default this is set
+			to false.
+
 	stacktrace	[FTRACE]
 			Enabled the stack tracer on boot up.
 
diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h
index 24d49c7..eafd9aa 100644
--- a/include/linux/stackdepot.h
+++ b/include/linux/stackdepot.h
@@ -21,4 +21,5 @@ unsigned int stack_depot_fetch(depot_stack_handle_t handle,
 
 unsigned int filter_irq_stacks(unsigned long *entries, unsigned int nr_entries);
 
+int stack_depot_init(void);
 #endif
diff --git a/init/main.c b/init/main.c
index 32b2a8a..8fcf9bb 100644
--- a/init/main.c
+++ b/init/main.c
@@ -98,6 +98,7 @@
 #include <linux/mem_encrypt.h>
 #include <linux/kcsan.h>
 #include <linux/init_syscalls.h>
+#include <linux/stackdepot.h>
 
 #include <asm/io.h>
 #include <asm/bugs.h>
@@ -827,6 +828,7 @@ static void __init mm_init(void)
 	page_ext_init_flatmem();
 	init_debug_pagealloc();
 	report_meminit();
+	stack_depot_init();
 	mem_init();
 	kmem_cache_init();
 	kmemleak_init();
diff --git a/lib/stackdepot.c b/lib/stackdepot.c
index dff8521..0398658 100644
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -31,6 +31,7 @@
 #include <linux/stackdepot.h>
 #include <linux/string.h>
 #include <linux/types.h>
+#include <linux/memblock.h>
 
 #define DEPOT_STACK_BITS (sizeof(depot_stack_handle_t) * 8)
 
@@ -146,9 +147,32 @@ static struct stack_record *depot_alloc_stack(unsigned long *entries, int size,
 #define STACK_HASH_MASK (STACK_HASH_SIZE - 1)
 #define STACK_HASH_SEED 0x9747b28c
 
-static struct stack_record *stack_table[STACK_HASH_SIZE] = {
-	[0 ...	STACK_HASH_SIZE - 1] = NULL
-};
+static bool stack_depot_disable;
+static struct stack_record **stack_table;
+
+static int __init is_stack_depot_disabled(char *str)
+{
+	kstrtobool(str, &stack_depot_disable);
+	if (stack_depot_disable) {
+		pr_info("Stack Depot is disabled\n");
+		stack_table = NULL;
+	}
+	return 0;
+}
+early_param("stack_depot_disable", is_stack_depot_disabled);
+
+int __init stack_depot_init(void)
+{
+	if (!stack_depot_disable) {
+		size_t size = (STACK_HASH_SIZE * sizeof(struct stack_record *));
+		int i;
+
+		stack_table = memblock_alloc(size, size);
+		for (i = 0; i < STACK_HASH_SIZE;  i++)
+			stack_table[i] = NULL;
+	}
+	return 0;
+}
 
 /* Calculate hash for a stack */
 static inline u32 hash_stack(unsigned long *entries, unsigned int size)
@@ -242,7 +266,7 @@ depot_stack_handle_t stack_depot_save(unsigned long *entries,
 	unsigned long flags;
 	u32 hash;
 
-	if (unlikely(nr_entries == 0))
+	if (unlikely(nr_entries == 0) || stack_depot_disable)
 		goto fast_exit;
 
 	hash = hash_stack(entries, nr_entries);
-- 
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation
2.7.4

Re: [PATCH v6 2/2] lib: stackdepot: Add support to disable stack depot

[Andrew Morton]

On Wed, 27 Jan 2021 17:36:38 +0530 vjitta@codeaurora.org wrote:

> Add a kernel parameter stack_depot_disable to disable
> stack depot. So that stack hash table doesn't consume
> any memory when stack depot is disabled.
> 
> The usecase is CONFIG_PAGE_OWNER without page_owner=on.
> Without this patch, stackdepot will consume the memory
> for the hashtable. By default, it's 8M which is never trivial.
> 
> With this option, in CONFIG_PAGE_OWNER configured system,
> page_owner=off, stack_depot_disable in kernel command line,
> we could save the wasted memory for the hashtable.

CONFIG_STACKDEPOT=n:

main.c:(.init.text+0x4c1): undefined reference to `stack_depot_init'


--- a/include/linux/stackdepot.h~lib-stackdepot-add-support-to-disable-stack-depot-fix
+++ a/include/linux/stackdepot.h
@@ -21,5 +21,13 @@ unsigned int stack_depot_fetch(depot_sta
 
 unsigned int filter_irq_stacks(unsigned long *entries, unsigned int nr_entries);
 
+#ifdef CONFIG_STACKDEPOT
 int stack_depot_init(void);
+#else
+static inline int stack_depot_init(void)
+{
+	return 0;
+}
+#endif	/* CONFIG_STACKDEPOT */
+
 #endif
_