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powerpc: Add VDSO version of time

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On 04/18/2013 07:38 PM, Anton Blanchard wrote:
> Since you are only reading one long you shouldn't need to check the
> update count and loop, you will always see a consistent value. The
> system call version of time() just does an unprotected load for example.

Fixed.

> With the above change and with Michael's comments covered (decent
> changelog entry and Signed-off-by):
>
> Acked-by: Anton Blanchard <anton@samba.org>

Thanks for the review, below the updated patch:

From: Adhemerval Zanella <azanella@linux.vnet.ibm.com>

This patch implement the time syscall as vDSO. The performance speedups
are:

Baseline PPC32: 380 nsec
Baseline PPC64: 350 nsec
vdso PPC32:      20 nsec
vsdo PPC64:      20 nsec

Tested on 64 bit build with both 32 bit and 64 bit userland.

Acked-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Adhemerval Zanella <azanella@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Adhemerval Zanella 2013-04-22 09:29:33 +00:00 committed by Benjamin Herrenschmidt
parent af81d7878c
commit fcb41a2030
5 changed files with 58 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
arch/powerpc/kernel/vdso.c
View File

@ -113,6 +113,10 @@ static struct vdso_patch_def vdso_patches[] = {
CPU_FTR_USE_TB, 0,
"__kernel_get_tbfreq", NULL
},
{
CPU_FTR_USE_TB, 0,
"__kernel_time", NULL
},
};
/*

26
arch/powerpc/kernel/vdso32/gettimeofday.S
View File

@ -180,6 +180,32 @@ V_FUNCTION_BEGIN(__kernel_clock_getres)
V_FUNCTION_END(__kernel_clock_getres)
/*
* Exact prototype of time()
*
* time_t time(time *t);
*
*/
V_FUNCTION_BEGIN(__kernel_time)
.cfi_startproc
mflr r12
.cfi_register lr,r12
mr r11,r3 /* r11 holds t */
bl __get_datapage@local
mr r9, r3 /* datapage ptr in r9 */
lwz r3,STAMP_XTIME+TSPEC_TV_SEC(r9)
cmplwi r11,0 /* check if t is NULL */
beq 2f
stw r3,0(r11) /* store result at *t */
2: mtlr r12
crclr cr0*4+so
blr
.cfi_endproc
V_FUNCTION_END(__kernel_time)
/*
* This is the core of clock_gettime() and gettimeofday(),
* it returns the current time in r3 (seconds) and r4.

1
arch/powerpc/kernel/vdso32/vdso32.lds.S
View File

@ -150,6 +150,7 @@ VERSION
#ifdef CONFIG_PPC64
__kernel_getcpu;
#endif
__kernel_time;
local: *;
};

26
arch/powerpc/kernel/vdso64/gettimeofday.S
View File

@ -164,6 +164,32 @@ V_FUNCTION_BEGIN(__kernel_clock_getres)
.cfi_endproc
V_FUNCTION_END(__kernel_clock_getres)
/*
* Exact prototype of time()
*
* time_t time(time *t);
*
*/
V_FUNCTION_BEGIN(__kernel_time)
.cfi_startproc
mflr r12
.cfi_register lr,r12
mr r11,r3 /* r11 holds t */
bl V_LOCAL_FUNC(__get_datapage)
ld r4,STAMP_XTIME+TSPC64_TV_SEC(r3)
cmpldi r11,0 /* check if t is NULL */
beq 2f
std r4,0(r11) /* store result at *t */
2: mtlr r12
crclr cr0*4+so
mr r3,r4
blr
.cfi_endproc
V_FUNCTION_END(__kernel_time)
/*
* This is the core of clock_gettime() and gettimeofday(),

1
arch/powerpc/kernel/vdso64/vdso64.lds.S
View File

@ -147,6 +147,7 @@ VERSION
__kernel_sync_dicache_p5;
__kernel_sigtramp_rt64;
__kernel_getcpu;
__kernel_time;
local: *;
};