[PATCH 2/3] fork: make number of cached stacks (vmapped) configurable using Kbuild

From: Hoeun Ryu
Date: Fri Feb 03 2017 - 10:39:45 EST


Introducing NR_VMAP_STACK_CACHE, the number of cached stacks for virtually
mapped kernel stack can be configurable using Kbuild system.
default value is 2.

Signed-off-by: Hoeun Ryu <hoeun.ryu@xxxxxxxxx>
---
arch/Kconfig | 8 ++++++++
kernel/fork.c | 2 +-
2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index d49a8e6..e94c432 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -849,6 +849,14 @@ config VMAP_STACK
the stack to map directly to the KASAN shadow map using a formula
that is incorrect if the stack is in vmalloc space.

+config NR_VMAP_STACK_CACHE
+ int "Number of cached stacks"
+ default "2"
+ depends on VMAP_STACK
+ ---help---
+ This determines how many stacks can be cached for virtually
+ mapped kernel stacks.
+
config ARCH_WANT_RELAX_ORDER
bool

diff --git a/kernel/fork.c b/kernel/fork.c
index 54421a9..50de6cf 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -166,7 +166,7 @@ void __weak arch_release_thread_stack(unsigned long *stack)
* vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
* flush. Try to minimize the number of calls by caching stacks.
*/
-#define NR_CACHED_STACKS 2
+#define NR_CACHED_STACKS CONFIG_NR_VMAP_STACK_CACHE

struct vm_stack_cache {
struct vm_struct **vm_stacks;
--
2.7.4