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From: Michael Ellerman <mpe@ellerman.id.au>
To: Christophe Leroy <christophe.leroy@c-s.fr>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Paul Mackerras <paulus@samba.org>
Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v3 4/8] powerpc/vdso32: inline __get_datapage()
Date: Thu, 28 Nov 2019 16:31:27 +1100	[thread overview]
Message-ID: <87sgm8zhw0.fsf@mpe.ellerman.id.au> (raw)
In-Reply-To: <dd5e359b-5864-f8e3-876a-ec606b51eb65@c-s.fr>

Christophe Leroy <christophe.leroy@c-s.fr> writes:
> Le 22/11/2019 à 07:38, Michael Ellerman a écrit :
>> Michael Ellerman <mpe@ellerman.id.au> writes:
>>> Christophe Leroy <christophe.leroy@c-s.fr> writes:
>>>> __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 <christophe.leroy@c-s.fr>
>>>
>>> This doesn't build with gcc 4.6.3:
>>>
>>>    /linux/arch/powerpc/kernel/vdso32/gettimeofday.S: Assembler messages:
>>>    /linux/arch/powerpc/kernel/vdso32/gettimeofday.S:41: Error: unsupported relocation against __kernel_datapage_offset
>>>    /linux/arch/powerpc/kernel/vdso32/gettimeofday.S:86: Error: unsupported relocation against __kernel_datapage_offset
>>>    /linux/arch/powerpc/kernel/vdso32/gettimeofday.S:213: Error: unsupported relocation against __kernel_datapage_offset
>>>    /linux/arch/powerpc/kernel/vdso32/gettimeofday.S:247: Error: unsupported relocation against __kernel_datapage_offset
>>>    make[4]: *** [arch/powerpc/kernel/vdso32/gettimeofday.o] Error 1
>> 
>> Actually I guess it's binutils, which is v2.22 in this case.
>> 
>> Needed this:
>> 
>> diff --git a/arch/powerpc/include/asm/vdso_datapage.h b/arch/powerpc/include/asm/vdso_datapage.h
>> index 12785f72f17d..0048db347ddf 100644
>> --- a/arch/powerpc/include/asm/vdso_datapage.h
>> +++ b/arch/powerpc/include/asm/vdso_datapage.h
>> @@ -117,7 +117,7 @@ extern struct vdso_data *vdso_data;
>>   .macro get_datapage ptr, tmp
>>   	bcl	20, 31, .+4
>>   	mflr	\ptr
>> -	addi	\ptr, \ptr, __kernel_datapage_offset - (.-4)
>> +	addi	\ptr, \ptr, (__kernel_datapage_offset - (.-4))@l
>>   	lwz	\tmp, 0(\ptr)
>>   	add	\ptr, \tmp, \ptr
>>   .endm
>> 
>
> Are you still planning to getting this series merged ? Do you need any 
> help / rebase / re-spin ?

Not sure. I'll possibly send a 2nd pull request next week with it
included.

cheers

  reply	other threads:[~2019-11-28  5:31 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-29  9:53 [PATCH v3 0/8] powerpc/vdso32 enhancement and optimisation Christophe Leroy
2019-10-29  9:53 ` [PATCH v3 1/8] powerpc/32: Add VDSO version of getcpu on non SMP Christophe Leroy
2019-10-29  9:53 ` [PATCH v3 2/8] powerpc/vdso32: Add support for CLOCK_{REALTIME/MONOTONIC}_COARSE Christophe Leroy
2019-11-20 12:42   ` Michael Ellerman
2019-11-20 15:17     ` Christophe Leroy
2019-11-20 23:53       ` Michael Ellerman
2019-10-29  9:53 ` [PATCH v3 3/8] powerpc: Fix vDSO clock_getres() Christophe Leroy
2019-10-29  9:53 ` [PATCH v3 4/8] powerpc/vdso32: inline __get_datapage() Christophe Leroy
2019-11-22  1:58   ` Michael Ellerman
2019-11-22  6:38     ` Michael Ellerman
2019-11-27 14:47       ` Christophe Leroy
2019-11-28  5:31         ` Michael Ellerman [this message]
2019-12-02  8:02           ` Christophe Leroy
2019-10-29  9:53 ` [PATCH v3 5/8] powerpc/vdso32: Don't read cache line size from the datapage on PPC32 Christophe Leroy
2019-10-29  9:53 ` [PATCH v3 6/8] powerpc/vdso32: use LOAD_REG_IMMEDIATE() Christophe Leroy
2019-10-29  9:53 ` [PATCH v3 7/8] powerpc/vdso32: implement clock_getres entirely Christophe Leroy
2019-10-29  9:53 ` [PATCH v3 8/8] powerpc/vdso32: miscellaneous optimisations Christophe Leroy

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