On 15/10/15 15:06, Mark Rutland wrote:
Hi,
I have fixed all the nits locally. Thanks for pointing them out.
config FORCE_MAX_ZONEORDER
int
default "14" if (ARM64_64K_PAGES && TRANSPARENT_HUGEPAGE)
+ default "12" if (ARM64_16K_PAGES && TRANSPARENT_HUGEPAGE)
default "11"
I'm a little lost here. How are these numbers derived?
I struggled to find the right value for 16K. Thanks to Steve Capper
for the following explanation. I will add it as a comment.
All allocations from the buddy allocator have to have compound order
strictly less than MAX_ORDER. i.e, the maximum allocation size is
(MAX_ORDER - 1) PAGES. To align with the transparent huge page size,
we get :
(MAX_ORDER - 1) + PAGE_SHIFT = PMD_SHIFT
Which gives us:
MAX_ORDER = PAGE_SHIFT - 3 + PAGE_SHIFT - PAGE_SHIFT + 1
= PAGE_SHIFT - 2
That raises an interesting question about the selection of the value
for 4K. Shouldn't that be 10 instead of 11 ?
Steve ?
-#ifdef CONFIG_ARM64_64K_PAGES
+#if defined(CONFIG_ARM64_64K_PAGES)
#define NR_FIX_BTMAPS 4
+#elif defined (CONFIG_ARM64_16K_PAGES)
+#define NR_FIX_BTMAPS 16
#else
#define NR_FIX_BTMAPS 64
#endif
We could include <linux/sizes.h> and simplify this to:
#define NR_FIX_BTMAPS (SZ_256K / PAGE_SIZE)
Which works for me locally.
Nice cleanup. I will pick that as a separate patch in the series.
diff --git a/arch/arm64/include/asm/thread_info.h
b/arch/arm64/include/asm/thread_info.h
index 5eac6a2..90c7ff2 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h
@@ -25,6 +25,8 @@
#ifdef CONFIG_ARM64_4K_PAGES
#define THREAD_SIZE_ORDER 2
+#elif defined(CONFIG_ARM64_16K_PAGES)
+#define THREAD_SIZE_ORDER 0
#endif
#define THREAD_SIZE 16384
The above looks correct.
As an open/general question, why do both THREAD_SIZE_ORDER and
THREAD_SIZE exist? One really should be defined in terms of the other.
I think its mainly for choosing the mechanism for stack allocation. If it
is a multiple of a page, you allocate a page. If not, uses a kmem_cache.
#define id_aa64mmfr0_tgran_shift ID_AA64MMFR0_TGRAN4_SHIFT
#define id_aa64mmfr0_tgran_on ID_AA64MMFR0_TGRAN4_ON
I assume you'll s/ON/SUPPORTED/ per comments in another thread.
Yes
Thanks
Suzuki
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