Re: [discuss] Re: [PATCH] adjust x86-64 watchdog tick calculation

[Dave Jones <davej@redhat.com>]

On Fri, May 13, 2005 at 06:56:33PM -0400, Lee Revell wrote:
 > On Sat, 2005-05-14 at 00:51 +0200, Pavel Machek wrote:
 > > Hi!
 > > 
 > > > > > > Because it kills machine when interrupt latency gets too high?
 > > > > > > Like reading battery status using i2c...
 > > > > > 
 > > > > > That's a bug in the I2C reader then. Don't shot the messenger for bad news.
 > > > > 
 > > > > Disagreed.
 > > > > 
 > > > > Linux is not real time OS. Perhaps some real-time constraints "may not
 > > > > spend > 100msec with interrupts disabled" would be healthy
 > > >              ^^^^
 > > > You mean "microseconds", right?  100ms will be perceived by the user as,
 > > > well, their machine freezing for 100ms...
 > > 
 > > I did mean miliseconds. IIRC current watchdog is at one second and it
 > > still triggers even in cases when operation just takes too long.
 > 
 > I thought there was an understanding that 1 ms would be the target for
 > desktop responsiveness.  So yes, disabling interrupts for more than 1ms
 > is considered a bug.
 > 
 > Why do you need to disable interrupts for 100ms to read the battery
 > status exactly?

On some unfortunate hardware, we can go away even longer whilst
the BIOS does various SMI voodoo.  It got so bad in some situations
that the maintainers of the gnome battery app lowered the frequency
at which the poll the acpi interface.

		Dave