2021-07-17 16:21:30

by Jisheng Zhang

Subject: [PATCH] riscv: enable GENERIC_FIND_FIRST_BIT

From: Jisheng Zhang <[email protected]>

riscv doesn't implement architecture-optimized bitsearching functions
such as find_first_{zero}_bit() etc.

When GENERIC_FIND_FIRST_BIT=n, find_first_bit() is implemented with
find_next_bit() which is less efficient. Enable GENERIC_FIND_FIRST_BIT
for riscv to get more optimized find_first_bit() implementation, an
initial test(lib/find_bit_benchmark) shows find_first_bit() performance
is improved by nearly 32%.

Signed-off-by: Jisheng Zhang <[email protected]>
---
arch/riscv/Kconfig | 1 +
1 file changed, 1 insertion(+)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 8fcceb8eda07..7ebc54c5c245 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -47,6 +47,7 @@ config RISCV
select GENERIC_ATOMIC64 if !64BIT
select GENERIC_CLOCKEVENTS_BROADCAST if SMP
select GENERIC_EARLY_IOREMAP
+ select GENERIC_FIND_FIRST_BIT
select GENERIC_GETTIMEOFDAY if HAVE_GENERIC_VDSO
select GENERIC_IOREMAP
select GENERIC_IRQ_MULTI_HANDLER
--
2.32.0

2021-09-08 17:46:25

by Jisheng Zhang

Subject: Re: [PATCH] riscv: enable GENERIC_FIND_FIRST_BIT

Hi Palmer,

On Sun, 18 Jul 2021 00:14:23 +0800
Jisheng Zhang wrote:

> From: Jisheng Zhang <[email protected]>
>
> riscv doesn't implement architecture-optimized bitsearching functions
> such as find_first_{zero}_bit() etc.
>
> When GENERIC_FIND_FIRST_BIT=n, find_first_bit() is implemented with
> find_next_bit() which is less efficient. Enable GENERIC_FIND_FIRST_BIT
> for riscv to get more optimized find_first_bit() implementation, an
> initial test(lib/find_bit_benchmark) shows find_first_bit() performance
> is improved by nearly 32%.

It seems this patch is missed. Is it possible to pick it up for 2nd 5.15-rc1 PR?

Thanks

>
> Signed-off-by: Jisheng Zhang <[email protected]>
> ---
> arch/riscv/Kconfig | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 8fcceb8eda07..7ebc54c5c245 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -47,6 +47,7 @@ config RISCV
> select GENERIC_ATOMIC64 if !64BIT
> select GENERIC_CLOCKEVENTS_BROADCAST if SMP
> select GENERIC_EARLY_IOREMAP
> + select GENERIC_FIND_FIRST_BIT
> select GENERIC_GETTIMEOFDAY if HAVE_GENERIC_VDSO
> select GENERIC_IOREMAP
> select GENERIC_IRQ_MULTI_HANDLER

2021-09-09 01:40:31

by Kefeng Wang

Subject: Re: [PATCH] riscv: enable GENERIC_FIND_FIRST_BIT

On 2021/9/8 23:04, Jisheng Zhang wrote:
> Hi Palmer,
>
> On Sun, 18 Jul 2021 00:14:23 +0800
> Jisheng Zhang wrote:
>
>> From: Jisheng Zhang <[email protected]>
>>
>> riscv doesn't implement architecture-optimized bitsearching functions
>> such as find_first_{zero}_bit() etc.
>>
>> When GENERIC_FIND_FIRST_BIT=n, find_first_bit() is implemented with
>> find_next_bit() which is less efficient. Enable GENERIC_FIND_FIRST_BIT
>> for riscv to get more optimized find_first_bit() implementation, an
>> initial test(lib/find_bit_benchmark) shows find_first_bit() performance
>> is improved by nearly 32%.
> It seems this patch is missed. Is it possible to pick it up for 2nd 5.15-rc1 PR?
>
> Thanks

It is enabled unconditionally by following commit

commit dbbccfe505ef8fae804677abf0564c1e07479102

Author: Yury Norov <[email protected]>
Date:   Tue Aug 24 09:59:56 2021 +1000

    arch: remove GENERIC_FIND_FIRST_BIT entirely

>
>> Signed-off-by: Jisheng Zhang <[email protected]>
>> ---
>> arch/riscv/Kconfig | 1 +
>> 1 file changed, 1 insertion(+)
>>
>> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
>> index 8fcceb8eda07..7ebc54c5c245 100644
>> --- a/arch/riscv/Kconfig
>> +++ b/arch/riscv/Kconfig
>> @@ -47,6 +47,7 @@ config RISCV
>> select GENERIC_ATOMIC64 if !64BIT
>> select GENERIC_CLOCKEVENTS_BROADCAST if SMP
>> select GENERIC_EARLY_IOREMAP
>> + select GENERIC_FIND_FIRST_BIT
>> select GENERIC_GETTIMEOFDAY if HAVE_GENERIC_VDSO
>> select GENERIC_IOREMAP
>> select GENERIC_IRQ_MULTI_HANDLER
>
>
> _______________________________________________
> linux-riscv mailing list
> [email protected]
> http://lists.infradead.org/mailman/listinfo/linux-riscv
> .
>

2021-09-09 14:41:40

by Jisheng Zhang

Subject: Re: [PATCH] riscv: enable GENERIC_FIND_FIRST_BIT

On Thu, 9 Sep 2021 08:58:31 +0800
Kefeng Wang <[email protected]> wrote:

> On 2021/9/8 23:04, Jisheng Zhang wrote:
> > Hi Palmer,
> >
> > On Sun, 18 Jul 2021 00:14:23 +0800
> > Jisheng Zhang wrote:
> >
> >> From: Jisheng Zhang <[email protected]>
> >>
> >> riscv doesn't implement architecture-optimized bitsearching functions
> >> such as find_first_{zero}_bit() etc.
> >>
> >> When GENERIC_FIND_FIRST_BIT=n, find_first_bit() is implemented with
> >> find_next_bit() which is less efficient. Enable GENERIC_FIND_FIRST_BIT
> >> for riscv to get more optimized find_first_bit() implementation, an
> >> initial test(lib/find_bit_benchmark) shows find_first_bit() performance
> >> is improved by nearly 32%.
> > It seems this patch is missed. Is it possible to pick it up for 2nd 5.15-rc1 PR?
> >
> > Thanks
>
> It is enabled unconditionally by following commit
>
> commit dbbccfe505ef8fae804677abf0564c1e07479102
>
> Author: Yury Norov <[email protected]>
> Date:   Tue Aug 24 09:59:56 2021 +1000
>
>     arch: remove GENERIC_FIND_FIRST_BIT entirely
>

Aha, thanks for the information. After Yury's commit, this patch
is useless now.

thanks