Messages in this thread Patch in this message | | | Date | Tue, 18 Oct 2011 16:29:10 -0700 | From | Tim Bird <> | Subject | [PATCH 1/3] ARM 4Kstacks: Add support for 4K kernel stacks to ARM |
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This saves 4K per kernel thread and user-space process. For systems with lots of threads, this can save 100s of K of memory.
Signed-off-by: Tim Bird <tim.bird@am.sony.com> --- arch/arm/Kconfig | 13 +++++++++++++ arch/arm/include/asm/thread_info.h | 7 ++++++- arch/arm/kernel/entry-header.S | 4 ++-- arch/arm/mm/proc-macros.S | 4 ++-- 4 files changed, 23 insertions(+), 5 deletions(-)
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 3146ed3..321ee11 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -1555,6 +1555,19 @@ config OABI_COMPAT UNPREDICTABLE (in fact it can be predicted that it won't work at all). If in doubt say Y.
+config 4KSTACKS + bool "Use 4K kernel stacks instead of 8K" + default n + help + This option will use less memory for each kernel stack in the + system, which can save potentially hundreds of kilobytes of memory. + It also helps reduce fragmentation in kernel memory. However, + it can be dangerous since not all kernel code paths are thrifty + in their use of the stack. Unless you have carefully monitored your + kernel stack usage and verified that your programs and kernel + usage patterns will not overflow 4K, you should leave this set + to N. + config ARCH_HAS_HOLES_MEMORYMODEL bool
diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h index 7b5cc8d..3021d06 100644 --- a/arch/arm/include/asm/thread_info.h +++ b/arch/arm/include/asm/thread_info.h @@ -15,8 +15,13 @@ #include <linux/compiler.h> #include <asm/fpstate.h>
+#ifndef CONFIG_4KSTACKS #define THREAD_SIZE_ORDER 1 -#define THREAD_SIZE 8192 +#else +#define THREAD_SIZE_ORDER 0 +#endif + +#define THREAD_SIZE (4096 << THREAD_SIZE_ORDER) #define THREAD_START_SP (THREAD_SIZE - 8)
#ifndef __ASSEMBLY__ diff --git a/arch/arm/kernel/entry-header.S b/arch/arm/kernel/entry-header.S index 9a8531e..c818505 100644 --- a/arch/arm/kernel/entry-header.S +++ b/arch/arm/kernel/entry-header.S @@ -109,8 +109,8 @@ .endm
.macro get_thread_info, rd - mov \rd, sp, lsr #13 - mov \rd, \rd, lsl #13 + mov \rd, sp, lsr #12 + THREAD_SIZE_ORDER + mov \rd, \rd, lsl #12 + THREAD_SIZE_ORDER .endm
@ diff --git a/arch/arm/mm/proc-macros.S b/arch/arm/mm/proc-macros.S index 307a4de..27c0907 100644 --- a/arch/arm/mm/proc-macros.S +++ b/arch/arm/mm/proc-macros.S @@ -30,8 +30,8 @@ * act_mm - get current->active_mm */ .macro act_mm, rd - bic \rd, sp, #8128 - bic \rd, \rd, #63 + mov \rd, sp, lsr #12 + THREAD_SIZE_ORDER + mov \rd, \rd, lsl #12 + THREAD_SIZE_ORDER ldr \rd, [\rd, #TI_TASK] ldr \rd, [\rd, #TSK_ACTIVE_MM] .endm -- 1.6.6
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