linux-kernel - Re: [PATCH 13/13] sh/irq: use seq_put_decimal_ull

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Message-ID: <57371ce2.3933.1937d47626c.Coremail.00107082@163.com>
Date: Sat, 30 Nov 2024 21:34:10 +0800 (CST)
From: "David Wang" <00107082@....com>
To: "John Paul Adrian Glaubitz" <glaubitz@...sik.fu-berlin.de>
Cc: ysato@...rs.sourceforge.jp, dalias@...c.org, linux-kernel@...r.kernel.org, 
	linux-sh@...r.kernel.org
Subject: Re: [PATCH 13/13] sh/irq: use seq_put_decimal_ull_width() for
 decimal values


At 2024-11-30 20:44:26, "John Paul Adrian Glaubitz" <glaubitz@...sik.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@....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