The patch titled
Subject: lib: stackdepot: add support to disable stack depot
has been added to the -mm tree. Its filename is
lib-stackdepot-add-support-to-disable-stack-depot.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/lib-stackdepot-add-support-to-disable-stack-depot.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/lib-stackdepot-add-support-to-disable-stack-depot.patch
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------------------------------------------------------
From: Vijayanand Jitta <vjitta@xxxxxxxxxxxxxx>
Subject: lib: stackdepot: add support to disable stack depot
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 use case 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.
Link: https://lkml.kernel.org/r/1611749198-24316-2-git-send-email-vjitta@xxxxxxxxxxxxxx
Signed-off-by: Vinayak Menon <vinmenon@xxxxxxxxxxxxxx>
Signed-off-by: Vijayanand Jitta <vjitta@xxxxxxxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Yogesh Lal <ylal@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
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(-)
--- a/Documentation/admin-guide/kernel-parameters.txt~lib-stackdepot-add-support-to-disable-stack-depot
+++ a/Documentation/admin-guide/kernel-parameters.txt
@@ -5132,6 +5132,12 @@
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.
--- a/include/linux/stackdepot.h~lib-stackdepot-add-support-to-disable-stack-depot
+++ a/include/linux/stackdepot.h
@@ -21,4 +21,5 @@ unsigned int stack_depot_fetch(depot_sta
unsigned int filter_irq_stacks(unsigned long *entries, unsigned int nr_entries);
+int stack_depot_init(void);
#endif
--- a/init/main.c~lib-stackdepot-add-support-to-disable-stack-depot
+++ a/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>
@@ -828,6 +829,7 @@ static void __init mm_init(void)
init_mem_debugging_and_hardening();
kfence_alloc_pool();
report_meminit();
+ stack_depot_init();
mem_init();
/* page_owner must be initialized after buddy is ready */
page_ext_init_flatmem_late();
--- a/lib/stackdepot.c~lib-stackdepot-add-support-to-disable-stack-depot
+++ a/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)
@@ -145,9 +146,32 @@ static struct stack_record *depot_alloc_
#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)
@@ -241,7 +265,7 @@ depot_stack_handle_t stack_depot_save(un
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);
_
Patches currently in -mm which might be from vjitta@xxxxxxxxxxxxxx are
lib-stackdepot-add-support-to-disable-stack-depot.patch
