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Commit fcb41a20 authored by Adhemerval Zanella's avatar Adhemerval Zanella Committed by Benjamin Herrenschmidt
Browse files

powerpc: Add VDSO version of time 



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: default avatarAnton 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: default avatarAnton Blanchard <anton@samba.org>
Signed-off-by: default avatarAdhemerval Zanella <azanella@linux.vnet.ibm.com>
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent af81d787

arch/powerpc/kernel/vdso.c

+4 −0
Original line number Diff line number Diff line
@@ -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

	},

};



/*

arch/powerpc/kernel/vdso32/gettimeofday.S

+26 −0
Original line number Diff line number Diff line
@@ -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.

arch/powerpc/kernel/vdso32/vdso32.lds.S

+1 −0
Original line number Diff line number Diff line
@@ -150,6 +150,7 @@ VERSION 
#ifdef CONFIG_PPC64

		__kernel_getcpu;

#endif

		__kernel_time;



	local: *;

	};

arch/powerpc/kernel/vdso64/gettimeofday.S

+26 −0
Original line number Diff line number Diff line
@@ -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(),

arch/powerpc/kernel/vdso64/vdso64.lds.S

+1 −0
Original line number Diff line number Diff line
@@ -147,6 +147,7 @@ VERSION 
		__kernel_sync_dicache_p5;

		__kernel_sigtramp_rt64;

		__kernel_getcpu;

		__kernel_time;



	local: *;

	};