__get_datapage() is only a few instructions to retrieve the
address of the page where the kernel stores data to the VDSO.
By inlining this function into its users, a bl/blr pair and
a mflr/mtlr pair is avoided, plus a few reg moves.
The improvement is noticeable (about 55 nsec/call on an 8xx)
vdsotest before the patch:
gettimeofday: vdso: 731 nsec/call
clock-gettime-realtime-coarse: vdso: 668 nsec/call
clock-gettime-monotonic-coarse: vdso: 745 nsec/call
vdsotest after the patch:
gettimeofday: vdso: 677 nsec/call
clock-gettime-realtime-coarse: vdso: 613 nsec/call
clock-gettime-monotonic-coarse: vdso: 690 nsec/call
Signed-off-by: Christophe Leroy <[email protected]>
---
arch/powerpc/kernel/vdso32/cacheflush.S | 10 +++++-----
arch/powerpc/kernel/vdso32/datapage.S | 29 ++++-------------------------
arch/powerpc/kernel/vdso32/datapage.h | 12 ++++++++++++
arch/powerpc/kernel/vdso32/gettimeofday.S | 11 +++++------
4 files changed, 26 insertions(+), 36 deletions(-)
create mode 100644 arch/powerpc/kernel/vdso32/datapage.h
diff --git a/arch/powerpc/kernel/vdso32/cacheflush.S b/arch/powerpc/kernel/vdso32/cacheflush.S
index 7f882e7b9f43..e9453837e4ee 100644
--- a/arch/powerpc/kernel/vdso32/cacheflush.S
+++ b/arch/powerpc/kernel/vdso32/cacheflush.S
@@ -10,6 +10,8 @@
#include <asm/vdso.h>
#include <asm/asm-offsets.h>
+#include "datapage.h"
+
.text
/*
@@ -24,14 +26,12 @@ V_FUNCTION_BEGIN(__kernel_sync_dicache)
.cfi_startproc
mflr r12
.cfi_register lr,r12
- mr r11,r3
- bl __get_datapage@local
+ get_datapage r10, r0
mtlr r12
- mr r10,r3
lwz r7,CFG_DCACHE_BLOCKSZ(r10)
addi r5,r7,-1
- andc r6,r11,r5 /* round low to line bdy */
+ andc r6,r3,r5 /* round low to line bdy */
subf r8,r6,r4 /* compute length */
add r8,r8,r5 /* ensure we get enough */
lwz r9,CFG_DCACHE_LOGBLOCKSZ(r10)
@@ -48,7 +48,7 @@ V_FUNCTION_BEGIN(__kernel_sync_dicache)
lwz r7,CFG_ICACHE_BLOCKSZ(r10)
addi r5,r7,-1
- andc r6,r11,r5 /* round low to line bdy */
+ andc r6,r3,r5 /* round low to line bdy */
subf r8,r6,r4 /* compute length */
add r8,r8,r5
lwz r9,CFG_ICACHE_LOGBLOCKSZ(r10)
diff --git a/arch/powerpc/kernel/vdso32/datapage.S b/arch/powerpc/kernel/vdso32/datapage.S
index 6984125b9fc0..d480d2d4a3fe 100644
--- a/arch/powerpc/kernel/vdso32/datapage.S
+++ b/arch/powerpc/kernel/vdso32/datapage.S
@@ -11,34 +11,13 @@
#include <asm/unistd.h>
#include <asm/vdso.h>
+#include "datapage.h"
+
.text
.global __kernel_datapage_offset;
__kernel_datapage_offset:
.long 0
-V_FUNCTION_BEGIN(__get_datapage)
- .cfi_startproc
- /* We don't want that exposed or overridable as we want other objects
- * to be able to bl directly to here
- */
- .protected __get_datapage
- .hidden __get_datapage
-
- mflr r0
- .cfi_register lr,r0
-
- bcl 20,31,data_page_branch
-data_page_branch:
- mflr r3
- mtlr r0
- addi r3, r3, __kernel_datapage_offset-data_page_branch
- lwz r0,0(r3)
- .cfi_restore lr
- add r3,r0,r3
- blr
- .cfi_endproc
-V_FUNCTION_END(__get_datapage)
-
/*
* void *__kernel_get_syscall_map(unsigned int *syscall_count) ;
*
@@ -53,7 +32,7 @@ V_FUNCTION_BEGIN(__kernel_get_syscall_map)
mflr r12
.cfi_register lr,r12
mr r4,r3
- bl __get_datapage@local
+ get_datapage r3, r0
mtlr r12
addi r3,r3,CFG_SYSCALL_MAP32
cmpli cr0,r4,0
@@ -74,7 +53,7 @@ V_FUNCTION_BEGIN(__kernel_get_tbfreq)
.cfi_startproc
mflr r12
.cfi_register lr,r12
- bl __get_datapage@local
+ get_datapage r3, r0
lwz r4,(CFG_TB_TICKS_PER_SEC + 4)(r3)
lwz r3,CFG_TB_TICKS_PER_SEC(r3)
mtlr r12
diff --git a/arch/powerpc/kernel/vdso32/datapage.h b/arch/powerpc/kernel/vdso32/datapage.h
new file mode 100644
index 000000000000..ad96256be090
--- /dev/null
+++ b/arch/powerpc/kernel/vdso32/datapage.h
@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+.macro get_datapage ptr, tmp
+ bcl 20,31,888f
+888:
+ mflr \ptr
+ addi \ptr, \ptr, __kernel_datapage_offset - 888b
+ lwz \tmp, 0(\ptr)
+ add \ptr, \tmp, \ptr
+.endm
+
+
diff --git a/arch/powerpc/kernel/vdso32/gettimeofday.S b/arch/powerpc/kernel/vdso32/gettimeofday.S
index e10098cde89c..91a58f01dcd5 100644
--- a/arch/powerpc/kernel/vdso32/gettimeofday.S
+++ b/arch/powerpc/kernel/vdso32/gettimeofday.S
@@ -12,6 +12,8 @@
#include <asm/asm-offsets.h>
#include <asm/unistd.h>
+#include "datapage.h"
+
/* Offset for the low 32-bit part of a field of long type */
#ifdef CONFIG_PPC64
#define LOPART 4
@@ -35,8 +37,7 @@ V_FUNCTION_BEGIN(__kernel_gettimeofday)
mr r10,r3 /* r10 saves tv */
mr r11,r4 /* r11 saves tz */
- bl __get_datapage@local /* get data page */
- mr r9, r3 /* datapage ptr in r9 */
+ get_datapage r9, r0
cmplwi r10,0 /* check if tv is NULL */
beq 3f
lis r7,1000000@ha /* load up USEC_PER_SEC */
@@ -82,8 +83,7 @@ V_FUNCTION_BEGIN(__kernel_clock_gettime)
mflr r12 /* r12 saves lr */
.cfi_register lr,r12
mr r11,r4 /* r11 saves tp */
- bl __get_datapage@local /* get data page */
- mr r9,r3 /* datapage ptr in r9 */
+ get_datapage r9, r0
lis r7,NSEC_PER_SEC@h /* want nanoseconds */
ori r7,r7,NSEC_PER_SEC@l
beq cr5,70f
@@ -235,8 +235,7 @@ V_FUNCTION_BEGIN(__kernel_time)
.cfi_register lr,r12
mr r11,r3 /* r11 holds t */
- bl __get_datapage@local
- mr r9, r3 /* datapage ptr in r9 */
+ get_datapage r9, r0
lwz r3,STAMP_XTIME+TSPEC_TV_SEC(r9)
--
2.13.3
On Fri, 2019-08-16 at 14:48 +0000, Christophe Leroy wrote:
> __get_datapage() is only a few instructions to retrieve the
> address of the page where the kernel stores data to the VDSO.
>
> By inlining this function into its users, a bl/blr pair and
> a mflr/mtlr pair is avoided, plus a few reg moves.
>
> The improvement is noticeable (about 55 nsec/call on an 8xx)
Interesting... would be worth doing the same on vdso64 no ?
> vdsotest before the patch:
> gettimeofday: vdso: 731 nsec/call
> clock-gettime-realtime-coarse: vdso: 668 nsec/call
> clock-gettime-monotonic-coarse: vdso: 745 nsec/call
>
> vdsotest after the patch:
> gettimeofday: vdso: 677 nsec/call
> clock-gettime-realtime-coarse: vdso: 613 nsec/call
> clock-gettime-monotonic-coarse: vdso: 690 nsec/call
>
> Signed-off-by: Christophe Leroy <[email protected]>
> ---
> arch/powerpc/kernel/vdso32/cacheflush.S | 10 +++++-----
> arch/powerpc/kernel/vdso32/datapage.S | 29 ++++-----------------
> --------
> arch/powerpc/kernel/vdso32/datapage.h | 12 ++++++++++++
> arch/powerpc/kernel/vdso32/gettimeofday.S | 11 +++++------
> 4 files changed, 26 insertions(+), 36 deletions(-)
> create mode 100644 arch/powerpc/kernel/vdso32/datapage.h
>
> diff --git a/arch/powerpc/kernel/vdso32/cacheflush.S
> b/arch/powerpc/kernel/vdso32/cacheflush.S
> index 7f882e7b9f43..e9453837e4ee 100644
> --- a/arch/powerpc/kernel/vdso32/cacheflush.S
> +++ b/arch/powerpc/kernel/vdso32/cacheflush.S
> @@ -10,6 +10,8 @@
> #include <asm/vdso.h>
> #include <asm/asm-offsets.h>
>
> +#include "datapage.h"
> +
> .text
>
> /*
> @@ -24,14 +26,12 @@ V_FUNCTION_BEGIN(__kernel_sync_dicache)
> .cfi_startproc
> mflr r12
> .cfi_register lr,r12
> - mr r11,r3
> - bl __get_datapage@local
> + get_datapage r10, r0
> mtlr r12
> - mr r10,r3
>
> lwz r7,CFG_DCACHE_BLOCKSZ(r10)
> addi r5,r7,-1
> - andc r6,r11,r5 /* round low to line bdy */
> + andc r6,r3,r5 /* round low to line bdy */
> subf r8,r6,r4 /* compute length */
> add r8,r8,r5 /* ensure we get enough */
> lwz r9,CFG_DCACHE_LOGBLOCKSZ(r10)
> @@ -48,7 +48,7 @@ V_FUNCTION_BEGIN(__kernel_sync_dicache)
>
> lwz r7,CFG_ICACHE_BLOCKSZ(r10)
> addi r5,r7,-1
> - andc r6,r11,r5 /* round low to line bdy */
> + andc r6,r3,r5 /* round low to line bdy */
> subf r8,r6,r4 /* compute length */
> add r8,r8,r5
> lwz r9,CFG_ICACHE_LOGBLOCKSZ(r10)
> diff --git a/arch/powerpc/kernel/vdso32/datapage.S
> b/arch/powerpc/kernel/vdso32/datapage.S
> index 6984125b9fc0..d480d2d4a3fe 100644
> --- a/arch/powerpc/kernel/vdso32/datapage.S
> +++ b/arch/powerpc/kernel/vdso32/datapage.S
> @@ -11,34 +11,13 @@
> #include <asm/unistd.h>
> #include <asm/vdso.h>
>
> +#include "datapage.h"
> +
> .text
> .global __kernel_datapage_offset;
> __kernel_datapage_offset:
> .long 0
>
> -V_FUNCTION_BEGIN(__get_datapage)
> - .cfi_startproc
> - /* We don't want that exposed or overridable as we want other
> objects
> - * to be able to bl directly to here
> - */
> - .protected __get_datapage
> - .hidden __get_datapage
> -
> - mflr r0
> - .cfi_register lr,r0
> -
> - bcl 20,31,data_page_branch
> -data_page_branch:
> - mflr r3
> - mtlr r0
> - addi r3, r3, __kernel_datapage_offset-data_page_branch
> - lwz r0,0(r3)
> - .cfi_restore lr
> - add r3,r0,r3
> - blr
> - .cfi_endproc
> -V_FUNCTION_END(__get_datapage)
> -
> /*
> * void *__kernel_get_syscall_map(unsigned int *syscall_count) ;
> *
> @@ -53,7 +32,7 @@ V_FUNCTION_BEGIN(__kernel_get_syscall_map)
> mflr r12
> .cfi_register lr,r12
> mr r4,r3
> - bl __get_datapage@local
> + get_datapage r3, r0
> mtlr r12
> addi r3,r3,CFG_SYSCALL_MAP32
> cmpli cr0,r4,0
> @@ -74,7 +53,7 @@ V_FUNCTION_BEGIN(__kernel_get_tbfreq)
> .cfi_startproc
> mflr r12
> .cfi_register lr,r12
> - bl __get_datapage@local
> + get_datapage r3, r0
> lwz r4,(CFG_TB_TICKS_PER_SEC + 4)(r3)
> lwz r3,CFG_TB_TICKS_PER_SEC(r3)
> mtlr r12
> diff --git a/arch/powerpc/kernel/vdso32/datapage.h
> b/arch/powerpc/kernel/vdso32/datapage.h
> new file mode 100644
> index 000000000000..ad96256be090
> --- /dev/null
> +++ b/arch/powerpc/kernel/vdso32/datapage.h
> @@ -0,0 +1,12 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +
> +.macro get_datapage ptr, tmp
> + bcl 20,31,888f
> +888:
> + mflr \ptr
> + addi \ptr, \ptr, __kernel_datapage_offset - 888b
> + lwz \tmp, 0(\ptr)
> + add \ptr, \tmp, \ptr
> +.endm
> +
> +
> diff --git a/arch/powerpc/kernel/vdso32/gettimeofday.S
> b/arch/powerpc/kernel/vdso32/gettimeofday.S
> index e10098cde89c..91a58f01dcd5 100644
> --- a/arch/powerpc/kernel/vdso32/gettimeofday.S
> +++ b/arch/powerpc/kernel/vdso32/gettimeofday.S
> @@ -12,6 +12,8 @@
> #include <asm/asm-offsets.h>
> #include <asm/unistd.h>
>
> +#include "datapage.h"
> +
> /* Offset for the low 32-bit part of a field of long type */
> #ifdef CONFIG_PPC64
> #define LOPART 4
> @@ -35,8 +37,7 @@ V_FUNCTION_BEGIN(__kernel_gettimeofday)
>
> mr r10,r3 /* r10 saves tv */
> mr r11,r4 /* r11 saves tz */
> - bl __get_datapage@local /* get data page */
> - mr r9, r3 /* datapage ptr in r9 */
> + get_datapage r9, r0
> cmplwi r10,0 /* check if tv is NULL */
> beq 3f
> lis r7,1000000@ha /* load up USEC_PER_SEC */
> @@ -82,8 +83,7 @@ V_FUNCTION_BEGIN(__kernel_clock_gettime)
> mflr r12 /* r12 saves lr */
> .cfi_register lr,r12
> mr r11,r4 /* r11 saves tp */
> - bl __get_datapage@local /* get data page */
> - mr r9,r3 /* datapage ptr in r9 */
> + get_datapage r9, r0
> lis r7,NSEC_PER_SEC@h /* want nanoseconds */
> ori r7,r7,NSEC_PER_SEC@l
> beq cr5,70f
> @@ -235,8 +235,7 @@ V_FUNCTION_BEGIN(__kernel_time)
> .cfi_register lr,r12
>
> mr r11,r3 /* r11 holds t */
> - bl __get_datapage@local
> - mr r9, r3 /* datapage ptr in r9 */
> + get_datapage r9, r0
>
> lwz r3,STAMP_XTIME+TSPEC_TV_SEC(r9)
>