"desktop" kernel parameter
Hello everyone, I just noticed the "desktop" kernel parameter on my menu.lst (SUSE 9.0). I did a search on Google but couldn't find that much. What does it affects? or if anyone can point me to the right direction I'll be glad. Many thanks. Jorge
On Wednesday 31 August 2005 04:00, Jorge Fábregas wrote:
Hello everyone,
I just noticed the "desktop" kernel parameter on my menu.lst (SUSE 9.0). I did a search on Google but couldn't find that much. What does it affects? or if anyone can point me to the right direction I'll be glad.
It affects the tick frequency (HZ) of the kernel, which is a count of the number of times per second the kernel stops and says "ok, what else needs to be done" With the desktop parameter, HZ is set to 1000, without it it's set to 100. Later kernels have it set to 1000 by default. The theory is that with HZ at 1000 instead of 100, the increased number of checkpoints where the kernel stops and sees if anything has happened increases the responsiveness of the system for a desktop user. The downside is that there is much more overhead, with 900 more interrupt handlers per second being called. I'm not sure if there has been a real study on the effectiveness of this, or the impact on a server where there are more long running jobs that don't need to be interrupted
Anders Johansson wrote:
On Wednesday 31 August 2005 04:00, Jorge Fábregas wrote:
Hello everyone,
I just noticed the "desktop" kernel parameter on my menu.lst (SUSE 9.0). I did a search on Google but couldn't find that much. What does it affects? or if anyone can point me to the right direction I'll be glad.
It affects the tick frequency (HZ) of the kernel, which is a count of the number of times per second the kernel stops and says "ok, what else needs to be done"
With the desktop parameter, HZ is set to 1000, without it it's set to 100. Later kernels have it set to 1000 by default.
The theory is that with HZ at 1000 instead of 100, the increased number of checkpoints where the kernel stops and sees if anything has happened increases the responsiveness of the system for a desktop user. The downside is that there is much more overhead, with 900 more interrupt handlers per second being called.
I'm not sure if there has been a real study on the effectiveness of this, or the impact on a server where there are more long running jobs that don't need to be interrupted
There have been some recent recommendations for different types of installations, 250Hz set in 2.6.13 on this box, whereas the recommendation for a laptop was 100Hz. Most of the discussion seemed to be around timeofday drift and there is work in progress to rewrite the kernel ntp. Using linux-2.6.13-rc6_timeofday-all.patch on both, this box with 250Hz is rock solid with the NTP server from 2.6.13-rc6 up to 2.6.13, whereas with 100Hz on the x86_64 laptop, I just checked a skew of about 48 seconds slow, perhaps I have a problem with ntp on the laptop as running rdate synched it up properly, tickadj=10000 on both. Regards Sid. -- Sid Boyce ... Hamradio License G3VBV, Keen licensed Private Pilot Retired IBM/Amdahl Mainframes and Sun/Fujitsu Servers Tech Support Specialist Microsoft Windows Free Zone - Linux used for all Computing Tasks
On Tuesday 30 August 2005 10:15 pm, Anders Johansson wrote: <snip>
I'm not sure if there has been a real study on the effectiveness of this, or the impact on a server where there are more long running jobs that don't need to be interrupted
Thank you Anders for the nice explanation :) Exactly what I wanted to know. Jorge
Jorge Fábregas wrote:
On Tuesday 30 August 2005 10:15 pm, Anders Johansson wrote: <snip>
I'm not sure if there has been a real study on the effectiveness of this, or the impact on a server where there are more long running jobs that don't need to be interrupted
I know that software is entirely different than hardware, but do you suppose that if you set your kernel Hz to match that of the system clock, it would be an optimum setting? Then the kernel would check on-beat with the system clock. James W
participants (4)
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Anders Johansson -
James Wright -
Jorge Fábregas -
Sid Boyce