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SubjectRe: 2.6.14-rc4-rt7

* Daniel Walker <> wrote:

> I found this latency ~5 minutes after boot up, no load . It looks like
> vgacon_scroll() has a memset like operation which can grow.

do you have PRINTK_IGNORE_LOGLEVEL enabled? If yes then much of the
printk code will run with interrupts disabled - hence non-preemptable.
PRINTK_IGNORE_LOGLEVEL is a debugging feature for developers. I have
added an extra explanation to the Kconfig, see below.


Index: linux/lib/Kconfig.debug
--- linux.orig/lib/Kconfig.debug
+++ linux/lib/Kconfig.debug
@@ -18,6 +18,11 @@ config PRINTK_IGNORE_LOGLEVEL
distributions disable kernel log messages during
certain phases of system startup.)

+ NOTE: this option also makes printk non-preemptible,
+ which might improve the output of debugging info or
+ crash info, but it might also cause latencies if your
+ kernel is printk-ing alot.
Normally you dont need or want this option.

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