2008-01-28 22:18:20

by Adrian Bunk

[permalink] [raw]
Subject: [2.6 patch] let LOG_BUF_SHIFT default to 17

16 kB is often no longer enough for a normal boot of an UP system.

And even less when people e.g. use suspend.

17 seems to be a more reasonable default for current kernels on current
hardware (it's just the default, anyone who is memory limited can
still lower it).

Signed-off-by: Adrian Bunk <[email protected]>

---
f02213e3c1cb90ec1c66227f037110d489f30bfd
diff --git a/init/Kconfig b/init/Kconfig
index 0eda68f..81a1255 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -272,17 +272,14 @@ config IKCONFIG_PROC
config LOG_BUF_SHIFT
int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
range 12 21
- default 17 if S390 || LOCKDEP
- default 16 if X86_NUMAQ || IA64
- default 15 if SMP
- default 14
+ default 17
help
Select kernel log buffer size as a power of 2.
- Defaults and Examples:
- 17 => 128 KB for S/390
- 16 => 64 KB for x86 NUMAQ or IA-64
- 15 => 32 KB for SMP
- 14 => 16 KB for uniprocessor
+ Examples:
+ 17 => 128 KB
+ 16 => 64 KB
+ 15 => 32 KB
+ 14 => 16 KB
13 => 8 KB
12 => 4 KB


2008-01-28 22:38:32

by Randy Dunlap

[permalink] [raw]
Subject: Re: [2.6 patch] let LOG_BUF_SHIFT default to 17

On Tue, 29 Jan 2008 00:12:23 +0200 Adrian Bunk wrote:

> 16 kB is often no longer enough for a normal boot of an UP system.

s/16/64/ then agreed.

Acked-by: Randy Dunlap <[email protected]>


> And even less when people e.g. use suspend.
>
> 17 seems to be a more reasonable default for current kernels on current
> hardware (it's just the default, anyone who is memory limited can
> still lower it).
>
> Signed-off-by: Adrian Bunk <[email protected]>
>
> ---
> f02213e3c1cb90ec1c66227f037110d489f30bfd
> diff --git a/init/Kconfig b/init/Kconfig
> index 0eda68f..81a1255 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -272,17 +272,14 @@ config IKCONFIG_PROC
> config LOG_BUF_SHIFT
> int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
> range 12 21
> - default 17 if S390 || LOCKDEP
> - default 16 if X86_NUMAQ || IA64
> - default 15 if SMP
> - default 14
> + default 17
> help
> Select kernel log buffer size as a power of 2.
> - Defaults and Examples:
> - 17 => 128 KB for S/390
> - 16 => 64 KB for x86 NUMAQ or IA-64
> - 15 => 32 KB for SMP
> - 14 => 16 KB for uniprocessor
> + Examples:
> + 17 => 128 KB
> + 16 => 64 KB
> + 15 => 32 KB
> + 14 => 16 KB
> 13 => 8 KB
> 12 => 4 KB
>
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
>


---
~Randy

2008-01-29 06:35:16

by Andi Kleen

[permalink] [raw]
Subject: Re: [2.6 patch] let LOG_BUF_SHIFT default to 17

Adrian Bunk <[email protected]> writes:

> 16 kB is often no longer enough for a normal boot of an UP system.

Better would be to just disable by default/remove noisy messages
to make the kernel boot output shorter.

I think we got a lot of IMHO useless messages in there.

-Andi

2008-01-29 07:35:49

by Adrian Bunk

[permalink] [raw]
Subject: Re: [2.6 patch] let LOG_BUF_SHIFT default to 17

On Tue, Jan 29, 2008 at 07:35:00AM +0100, Andi Kleen wrote:
> Adrian Bunk <[email protected]> writes:
>
> > 16 kB is often no longer enough for a normal boot of an UP system.
>
> Better would be to just disable by default/remove noisy messages
> to make the kernel boot output shorter.
>
> I think we got a lot of IMHO useless messages in there.

Nearly 25% of the messages in my dmesg come from ACPI.

Plus many other messages that cover these generic resources stuff (e.g.
BIOS map or ioport/iomem reservations).

All of these tend to be of great help when debugging driver regressions,
since diff'ing the dmesg's often is enough for determining whether it's
a driver problem or a PCI/ACPI/whatever problem.

> -Andi

cu
Adrian

--

"Is there not promise of rain?" Ling Tan asked suddenly out
of the darkness. There had been need of rain for many days.
"Only a promise," Lao Er said.
Pearl S. Buck - Dragon Seed

2008-02-01 16:20:26

by Ingo Molnar

[permalink] [raw]
Subject: Re: [2.6 patch] let LOG_BUF_SHIFT default to 17


* Adrian Bunk <[email protected]> wrote:

> 16 kB is often no longer enough for a normal boot of an UP system.
>
> And even less when people e.g. use suspend.
>
> 17 seems to be a more reasonable default for current kernels on
> current hardware (it's just the default, anyone who is memory limited
> can still lower it).

agreed - but i think the default should be even higher. Many reported
dmesg's are truncated at the really interesting bits so it's a real
problem in practice.

Ingo

2008-02-11 22:42:52

by Adrian Bunk

[permalink] [raw]
Subject: Re: [2.6 patch] let LOG_BUF_SHIFT default to 17

On Fri, Feb 01, 2008 at 05:20:03PM +0100, Ingo Molnar wrote:
>
> * Adrian Bunk <[email protected]> wrote:
>
> > 16 kB is often no longer enough for a normal boot of an UP system.
> >
> > And even less when people e.g. use suspend.
> >
> > 17 seems to be a more reasonable default for current kernels on
> > current hardware (it's just the default, anyone who is memory limited
> > can still lower it).
>
> agreed - but i think the default should be even higher. Many reported
> dmesg's are truncated at the really interesting bits so it's a real
> problem in practice.

17 is 128 kB.

Do we really have that many truncated dmesg's with LOG_BUF_SHIFT=17?

> Ingo

cu
Adrian

--

"Is there not promise of rain?" Ling Tan asked suddenly out
of the darkness. There had been need of rain for many days.
"Only a promise," Lao Er said.
Pearl S. Buck - Dragon Seed