[PATCH 13/13] sh/irq: use seq_put_decimal_ull_width() for decimal values

[PATCH 13/13] sh/irq: use seq_put_decimal_ull_width() for decimal values

[David Wang]

Performance improvement for reading /proc/interrupts on arch sh

Signed-off-by: David Wang <00107082@163.com>
---
 arch/sh/kernel/irq.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/sh/kernel/irq.c b/arch/sh/kernel/irq.c
index 4e6835de54cf..9022d8af9d68 100644
--- a/arch/sh/kernel/irq.c
+++ b/arch/sh/kernel/irq.c
@@ -43,9 +43,9 @@ int arch_show_interrupts(struct seq_file *p, int prec)
 {
 	int j;
 
-	seq_printf(p, "%*s: ", prec, "NMI");
+	seq_printf(p, "%*s:", prec, "NMI");
 	for_each_online_cpu(j)
-		seq_printf(p, "%10u ", per_cpu(irq_stat.__nmi_count, j));
+		seq_put_decimal_ull_width(p, " ", per_cpu(irq_stat.__nmi_count, j), 10);
 	seq_printf(p, "  Non-maskable interrupts\n");
 
 	seq_printf(p, "%*s: %10u\n", prec, "ERR", atomic_read(&irq_err_count));
-- 
2.39.2

Re: [PATCH 13/13] sh/irq: use seq_put_decimal_ull_width() for decimal values

[John Paul Adrian Glaubitz]

Hi David,

On Sat, 2024-11-09 at 00:26 +0800, David Wang wrote:
> Performance improvement for reading /proc/interrupts on arch sh
> 
> Signed-off-by: David Wang <00107082@163.com>
> ---
>  arch/sh/kernel/irq.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/sh/kernel/irq.c b/arch/sh/kernel/irq.c
> index 4e6835de54cf..9022d8af9d68 100644
> --- a/arch/sh/kernel/irq.c
> +++ b/arch/sh/kernel/irq.c
> @@ -43,9 +43,9 @@ int arch_show_interrupts(struct seq_file *p, int prec)
>  {
>  	int j;
>  
> -	seq_printf(p, "%*s: ", prec, "NMI");
> +	seq_printf(p, "%*s:", prec, "NMI");
>  	for_each_online_cpu(j)
> -		seq_printf(p, "%10u ", per_cpu(irq_stat.__nmi_count, j));
> +		seq_put_decimal_ull_width(p, " ", per_cpu(irq_stat.__nmi_count, j), 10);
>  	seq_printf(p, "  Non-maskable interrupts\n");
>  
>  	seq_printf(p, "%*s: %10u\n", prec, "ERR", atomic_read(&irq_err_count));

Sorry for the very late reply!

I don't quite understand why seq_put_decimal_ull_width() should be faster than seq_printf().

Can you elaborate on this a bit more?

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer
`. `'   Physicist
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913

Re: [PATCH 13/13] sh/irq: use seq_put_decimal_ull_width() for decimal values

[John Paul Adrian Glaubitz]

Hi David,

On Sat, 2024-11-30 at 13:41 +0100, John Paul Adrian Glaubitz wrote:
> On Sat, 2024-11-09 at 00:26 +0800, David Wang wrote:
> > Performance improvement for reading /proc/interrupts on arch sh
> > 
> > Signed-off-by: David Wang <00107082@163.com>
> > ---
> >  arch/sh/kernel/irq.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/arch/sh/kernel/irq.c b/arch/sh/kernel/irq.c
> > index 4e6835de54cf..9022d8af9d68 100644
> > --- a/arch/sh/kernel/irq.c
> > +++ b/arch/sh/kernel/irq.c
> > @@ -43,9 +43,9 @@ int arch_show_interrupts(struct seq_file *p, int prec)
> >  {
> >  	int j;
> >  
> > -	seq_printf(p, "%*s: ", prec, "NMI");
> > +	seq_printf(p, "%*s:", prec, "NMI");
> >  	for_each_online_cpu(j)
> > -		seq_printf(p, "%10u ", per_cpu(irq_stat.__nmi_count, j));
> > +		seq_put_decimal_ull_width(p, " ", per_cpu(irq_stat.__nmi_count, j), 10);
> >  	seq_printf(p, "  Non-maskable interrupts\n");
> >  
> >  	seq_printf(p, "%*s: %10u\n", prec, "ERR", atomic_read(&irq_err_count));
> 
> Sorry for the very late reply!
> 
> I don't quite understand why seq_put_decimal_ull_width() should be faster than seq_printf().
> 
> Can you elaborate on this a bit more?

I just checked existing merges of this patch for other architectures which include
a more elaborate patch description. If you could do that for SH as well, I can pick
the patch for v6.14.

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer
`. `'   Physicist
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913

Re: [PATCH 13/13] sh/irq: use seq_put_decimal_ull_width() for decimal values

[David Wang]

At 2024-11-30 20:44:26, "John Paul Adrian Glaubitz" <glaubitz@physik.fu-berlin.de> wrote:
>Hi David,
>
>On Sat, 2024-11-30 at 13:41 +0100, John Paul Adrian Glaubitz wrote:
>> On Sat, 2024-11-09 at 00:26 +0800, David Wang wrote:
>> > Performance improvement for reading /proc/interrupts on arch sh
>> > 
>> > Signed-off-by: David Wang <00107082@163.com>
>> > ---
>> >  arch/sh/kernel/irq.c | 4 ++--
>> >  1 file changed, 2 insertions(+), 2 deletions(-)
>> > 
>> > diff --git a/arch/sh/kernel/irq.c b/arch/sh/kernel/irq.c
>> > index 4e6835de54cf..9022d8af9d68 100644
>> > --- a/arch/sh/kernel/irq.c
>> > +++ b/arch/sh/kernel/irq.c
>> > @@ -43,9 +43,9 @@ int arch_show_interrupts(struct seq_file *p, int prec)
>> >  {
>> >  	int j;
>> >  
>> > -	seq_printf(p, "%*s: ", prec, "NMI");
>> > +	seq_printf(p, "%*s:", prec, "NMI");
>> >  	for_each_online_cpu(j)
>> > -		seq_printf(p, "%10u ", per_cpu(irq_stat.__nmi_count, j));
>> > +		seq_put_decimal_ull_width(p, " ", per_cpu(irq_stat.__nmi_count, j), 10);
>> >  	seq_printf(p, "  Non-maskable interrupts\n");
>> >  
>> >  	seq_printf(p, "%*s: %10u\n", prec, "ERR", atomic_read(&irq_err_count));
>> 
>> Sorry for the very late reply!
>> 
>> I don't quite understand why seq_put_decimal_ull_width() should be faster than seq_printf().
>> 
>> Can you elaborate on this a bit more?
>
>I just checked existing merges of this patch for other architectures which include
>a more elaborate patch description. If you could do that for SH as well, I can pick
>the patch for v6.14.
>
>Adrian
>
>-- 
> .''`.  John Paul Adrian Glaubitz
>: :' :  Debian Developer
>`. `'   Physicist
>  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913

Sure, I will make the change.

To be honest, I do not have a SH platform to confirm the performance changes.
If convenient, a simple `strace -T -e read cat /proc/interrupts > /dev/null`
can be used to verify any improvement, and the core change in commit
f9ed1f7c2e26fcd1978(genirq/proc: Use seq_put_decimal_ull_width() for decimal values)
is needed.


Thanks
David

[PATCH v2] sh/irq: use seq_put_decimal_ull_width() for decimal values

[David Wang]

On a system with n CPUs and m interrupts, there will be n*m decimal
values yielded via seq_printf(.."%10u "..) which has significant costs
parsing format string and is less efficient than
seq_put_decimal_ull_width(). Stress reading /proc/interrupts
indicates ~30% performance improvement with this patch.

Signed-off-by: David Wang <00107082@163.com>
---
 arch/sh/kernel/irq.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/sh/kernel/irq.c b/arch/sh/kernel/irq.c
index 4e6835de54cf..9022d8af9d68 100644
--- a/arch/sh/kernel/irq.c
+++ b/arch/sh/kernel/irq.c
@@ -43,9 +43,9 @@ int arch_show_interrupts(struct seq_file *p, int prec)
 {
 	int j;
 
-	seq_printf(p, "%*s: ", prec, "NMI");
+	seq_printf(p, "%*s:", prec, "NMI");
 	for_each_online_cpu(j)
-		seq_printf(p, "%10u ", per_cpu(irq_stat.__nmi_count, j));
+		seq_put_decimal_ull_width(p, " ", per_cpu(irq_stat.__nmi_count, j), 10);
 	seq_printf(p, "  Non-maskable interrupts\n");
 
 	seq_printf(p, "%*s: %10u\n", prec, "ERR", atomic_read(&irq_err_count));
-- 
2.39.2

Re: [PATCH v2] sh/irq: use seq_put_decimal_ull_width() for decimal values

[John Paul Adrian Glaubitz]

Hi David,

On Sat, 2024-11-30 at 21:49 +0800, David Wang wrote:
> On a system with n CPUs and m interrupts, there will be n*m decimal
> values yielded via seq_printf(.."%10u "..) which has significant costs
> parsing format string and is less efficient than
> seq_put_decimal_ull_width(). Stress reading /proc/interrupts
> indicates ~30% performance improvement with this patch.
> 
> Signed-off-by: David Wang <00107082@163.com>
> ---
>  arch/sh/kernel/irq.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/sh/kernel/irq.c b/arch/sh/kernel/irq.c
> index 4e6835de54cf..9022d8af9d68 100644
> --- a/arch/sh/kernel/irq.c
> +++ b/arch/sh/kernel/irq.c
> @@ -43,9 +43,9 @@ int arch_show_interrupts(struct seq_file *p, int prec)
>  {
>  	int j;
>  
> -	seq_printf(p, "%*s: ", prec, "NMI");
> +	seq_printf(p, "%*s:", prec, "NMI");
>  	for_each_online_cpu(j)
> -		seq_printf(p, "%10u ", per_cpu(irq_stat.__nmi_count, j));
> +		seq_put_decimal_ull_width(p, " ", per_cpu(irq_stat.__nmi_count, j), 10);
>  	seq_printf(p, "  Non-maskable interrupts\n");
>  
>  	seq_printf(p, "%*s: %10u\n", prec, "ERR", atomic_read(&irq_err_count));

Reviewed-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>

Thanks,
Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer
`. `'   Physicist
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913