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Date: Tue, 05 Jan 2010 10:19:31 +0900
From: Tejun Heo <tj@...nel.org>
To: Christoph Lameter <cl@...ux-foundation.org>
CC: linux-kernel@...r.kernel.org, Mel Gorman <mel@....ul.ie>,
Pekka Enberg <penberg@...helsinki.fi>,
Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Subject: Re: [this_cpu_xx V9 4/7] Generic inc / dec percpu instructions
On 01/05/2010 07:34 AM, Christoph Lameter wrote:
> Optimize code generated for percpu access by checking for increment and
> decrements.
>
> Signed-off-by: Christoph Lameter <cl@...ux-foundation.org>
>
> ---
> arch/x86/include/asm/percpu.h | 100 ++++++++++++++++++++++++++++++++++++------
> 1 file changed, 86 insertions(+), 14 deletions(-)
>
> Index: linux-2.6/arch/x86/include/asm/percpu.h
> ===================================================================
> --- linux-2.6.orig/arch/x86/include/asm/percpu.h 2010-01-04 15:33:02.000000000 -0600
> +++ linux-2.6/arch/x86/include/asm/percpu.h 2010-01-04 16:11:29.000000000 -0600
> @@ -104,6 +104,78 @@ do { \
> } \
> } while (0)
>
> +/*
> + * Generate a percpu add to memory instruction and optimize code
> + * if a one is added or subtracted.
> + */
> +#define percpu_add_op(var, val) \
> +do { \
> + typedef typeof(var) pto_T__; \
> + if (0) { \
> + pto_T__ pto_tmp__; \
> + pto_tmp__ = (val); \
> + } \
> + switch (sizeof(var)) { \
> + case 1: \
> + if (__builtin_constant_p(val) == 1) \
According to gcc doc, __builtin_constant_p() returns 1 on constant and
0 if not. It doesn't return the original expression. I'll commit the
following updated version after testing.
Thanks.
From: Christoph Lameter <cl@...ux-foundation.org>
Optimize code generated for percpu access by checking for increment and
decrements.
tj: fix incorrect usage of __builtin_constant_p() and restructure
percpu_add_op() macro.
Signed-off-by: Christoph Lameter <cl@...ux-foundation.org>
Signed-off-by: Tejun Heo <tj@...nel.org>
---
arch/x86/include/asm/percpu.h | 86 +++++++++++++++++++++++++++++++++++-------
1 file changed, 72 insertions(+), 14 deletions(-)
Index: percpu/arch/x86/include/asm/percpu.h
===================================================================
--- percpu.orig/arch/x86/include/asm/percpu.h
+++ percpu/arch/x86/include/asm/percpu.h
@@ -103,6 +103,64 @@ do { \
} \
} while (0)
+/*
+ * Generate a percpu add to memory instruction and optimize code
+ * if a one is added or subtracted.
+ */
+#define percpu_add_op(var, val) \
+do { \
+ typedef typeof(var) pao_T__; \
+ const int pao_ID__ = (__builtin_constant_p(val) && \
+ ((val) == 1 || (val) == -1)) ? (val) : 0; \
+ if (0) { \
+ pao_T__ pao_tmp__; \
+ pao_tmp__ = (val); \
+ } \
+ switch (sizeof(var)) { \
+ case 1: \
+ if (pao_ID__ == 1) \
+ asm("incb "__percpu_arg(0) : "+m" (var)); \
+ else if (pao_ID__ == -1) \
+ asm("decb "__percpu_arg(0) : "+m" (var)); \
+ else \
+ asm("addb %1, "__percpu_arg(0) \
+ : "+m" (var) \
+ : "qi" ((pao_T__)(val))); \
+ break; \
+ case 2: \
+ if (pao_ID__ == 1) \
+ asm("incw "__percpu_arg(0) : "+m" (var)); \
+ else if (pao_ID__ == -1) \
+ asm("decw "__percpu_arg(0) : "+m" (var)); \
+ else \
+ asm("addw %1, "__percpu_arg(0) \
+ : "+m" (var) \
+ : "ri" ((pao_T__)(val))); \
+ break; \
+ case 4: \
+ if (pao_ID__ == 1) \
+ asm("incl "__percpu_arg(0) : "+m" (var)); \
+ else if (pao_ID__ == -1) \
+ asm("decl "__percpu_arg(0) : "+m" (var)); \
+ else \
+ asm("addl %1, "__percpu_arg(0) \
+ : "+m" (var) \
+ : "ri" ((pao_T__)(val))); \
+ break; \
+ case 8: \
+ if (pao_ID__ == 1) \
+ asm("incq "__percpu_arg(0) : "+m" (var)); \
+ else if (pao_ID__ == -1) \
+ asm("decq "__percpu_arg(0) : "+m" (var)); \
+ else \
+ asm("addq %1, "__percpu_arg(0) \
+ : "+m" (var) \
+ : "re" ((pao_T__)(val))); \
+ break; \
+ default: __bad_percpu_size(); \
+ } \
+} while (0)
+
#define percpu_from_op(op, var, constraint) \
({ \
typeof(var) pfo_ret__; \
@@ -144,8 +202,8 @@ do { \
#define percpu_read(var) percpu_from_op("mov", var, "m" (var))
#define percpu_read_stable(var) percpu_from_op("mov", var, "p" (&(var)))
#define percpu_write(var, val) percpu_to_op("mov", var, val)
-#define percpu_add(var, val) percpu_to_op("add", var, val)
-#define percpu_sub(var, val) percpu_to_op("sub", var, val)
+#define percpu_add(var, val) percpu_add_op(var, val)
+#define percpu_sub(var, val) percpu_add_op(var, -(val))
#define percpu_and(var, val) percpu_to_op("and", var, val)
#define percpu_or(var, val) percpu_to_op("or", var, val)
#define percpu_xor(var, val) percpu_to_op("xor", var, val)
@@ -157,9 +215,9 @@ do { \
#define __this_cpu_write_1(pcp, val) percpu_to_op("mov", (pcp), val)
#define __this_cpu_write_2(pcp, val) percpu_to_op("mov", (pcp), val)
#define __this_cpu_write_4(pcp, val) percpu_to_op("mov", (pcp), val)
-#define __this_cpu_add_1(pcp, val) percpu_to_op("add", (pcp), val)
-#define __this_cpu_add_2(pcp, val) percpu_to_op("add", (pcp), val)
-#define __this_cpu_add_4(pcp, val) percpu_to_op("add", (pcp), val)
+#define __this_cpu_add_1(pcp, val) percpu_add_op((pcp), val)
+#define __this_cpu_add_2(pcp, val) percpu_add_op((pcp), val)
+#define __this_cpu_add_4(pcp, val) percpu_add_op((pcp), val)
#define __this_cpu_and_1(pcp, val) percpu_to_op("and", (pcp), val)
#define __this_cpu_and_2(pcp, val) percpu_to_op("and", (pcp), val)
#define __this_cpu_and_4(pcp, val) percpu_to_op("and", (pcp), val)
@@ -176,9 +234,9 @@ do { \
#define this_cpu_write_1(pcp, val) percpu_to_op("mov", (pcp), val)
#define this_cpu_write_2(pcp, val) percpu_to_op("mov", (pcp), val)
#define this_cpu_write_4(pcp, val) percpu_to_op("mov", (pcp), val)
-#define this_cpu_add_1(pcp, val) percpu_to_op("add", (pcp), val)
-#define this_cpu_add_2(pcp, val) percpu_to_op("add", (pcp), val)
-#define this_cpu_add_4(pcp, val) percpu_to_op("add", (pcp), val)
+#define this_cpu_add_1(pcp, val) percpu_add_op((pcp), val)
+#define this_cpu_add_2(pcp, val) percpu_add_op((pcp), val)
+#define this_cpu_add_4(pcp, val) percpu_add_op((pcp), val)
#define this_cpu_and_1(pcp, val) percpu_to_op("and", (pcp), val)
#define this_cpu_and_2(pcp, val) percpu_to_op("and", (pcp), val)
#define this_cpu_and_4(pcp, val) percpu_to_op("and", (pcp), val)
@@ -189,9 +247,9 @@ do { \
#define this_cpu_xor_2(pcp, val) percpu_to_op("xor", (pcp), val)
#define this_cpu_xor_4(pcp, val) percpu_to_op("xor", (pcp), val)
-#define irqsafe_cpu_add_1(pcp, val) percpu_to_op("add", (pcp), val)
-#define irqsafe_cpu_add_2(pcp, val) percpu_to_op("add", (pcp), val)
-#define irqsafe_cpu_add_4(pcp, val) percpu_to_op("add", (pcp), val)
+#define irqsafe_cpu_add_1(pcp, val) percpu_add_op((pcp), val)
+#define irqsafe_cpu_add_2(pcp, val) percpu_add_op((pcp), val)
+#define irqsafe_cpu_add_4(pcp, val) percpu_add_op((pcp), val)
#define irqsafe_cpu_and_1(pcp, val) percpu_to_op("and", (pcp), val)
#define irqsafe_cpu_and_2(pcp, val) percpu_to_op("and", (pcp), val)
#define irqsafe_cpu_and_4(pcp, val) percpu_to_op("and", (pcp), val)
@@ -209,19 +267,19 @@ do { \
#ifdef CONFIG_X86_64
#define __this_cpu_read_8(pcp) percpu_from_op("mov", (pcp), "m"(pcp))
#define __this_cpu_write_8(pcp, val) percpu_to_op("mov", (pcp), val)
-#define __this_cpu_add_8(pcp, val) percpu_to_op("add", (pcp), val)
+#define __this_cpu_add_8(pcp, val) percpu_add_op((pcp), val)
#define __this_cpu_and_8(pcp, val) percpu_to_op("and", (pcp), val)
#define __this_cpu_or_8(pcp, val) percpu_to_op("or", (pcp), val)
#define __this_cpu_xor_8(pcp, val) percpu_to_op("xor", (pcp), val)
#define this_cpu_read_8(pcp) percpu_from_op("mov", (pcp), "m"(pcp))
#define this_cpu_write_8(pcp, val) percpu_to_op("mov", (pcp), val)
-#define this_cpu_add_8(pcp, val) percpu_to_op("add", (pcp), val)
+#define this_cpu_add_8(pcp, val) percpu_add_op((pcp), val)
#define this_cpu_and_8(pcp, val) percpu_to_op("and", (pcp), val)
#define this_cpu_or_8(pcp, val) percpu_to_op("or", (pcp), val)
#define this_cpu_xor_8(pcp, val) percpu_to_op("xor", (pcp), val)
-#define irqsafe_cpu_add_8(pcp, val) percpu_to_op("add", (pcp), val)
+#define irqsafe_cpu_add_8(pcp, val) percpu_add_op((pcp), val)
#define irqsafe_cpu_and_8(pcp, val) percpu_to_op("and", (pcp), val)
#define irqsafe_cpu_or_8(pcp, val) percpu_to_op("or", (pcp), val)
#define irqsafe_cpu_xor_8(pcp, val) percpu_to_op("xor", (pcp), val)
--
tejun
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