Linked by Thom Holwerda on Sun 22nd Apr 2007 22:47 UTC
Linux Ingo Molnar released a new patchset titled the 'Modular Scheduler Core and Completely Fair Scheduler'. He explained, "this project is a complete rewrite of the Linux task scheduler. My goal is to address various feature requests and to fix deficiencies in the vanilla scheduler that were suggested/found in the past few years, both for desktop scheduling and for server scheduling workloads."
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Virtualization
by Alexey Technologov on Mon 23rd Apr 2007 02:49 UTC
Alexey Technologov
Member since:
2007-03-16

How about Virtualization/Emulation software ?

I know that Linux kernels with HZ=1000 option are rather slow in Virtualization environments and I would like to know how this new scheduler will perform in such Virtual (VMware/VirtualBox/...) environments.

Reply Score: 1

RE: Virtualization
by MighMoS on Mon 23rd Apr 2007 03:40 in reply to "Virtualization"
MighMoS Member since:
2006-07-15

I am by no means an expert on any of this, but my guess would be that if a schedular is completely fair, then virtualization wouldn't be too good off, as the virtualized box would get one tick / whatever, no exceptions. All the processes in that box would have to run off that one tick (basically).

Of course, I could be completely wrong, in that case ignore me.

Reply Parent Score: 1

RE[2]: Virtualization
by thecwin on Tue 24th Apr 2007 17:29 in reply to "RE: Virtualization"
thecwin Member since:
2006-01-04

When they say "Completely fair", they actually mean more fair than equal. The processor time is divided in a fair way so that latency sensitive apps can be prioritised over more throughput apps. What you have described is equal timeslices (except nobody divides it as small as single ticks) which can be used on the current kernel, I believe.

Reply Parent Score: 1

RE: Virtualization
by sbergman27 on Mon 23rd Apr 2007 03:54 in reply to "Virtualization"
sbergman27 Member since:
2005-07-24

"""
I know that Linux kernels with HZ=1000 option are rather slow in Virtualization environments and I would like to know how this new scheduler will perform in such Virtual (VMware/VirtualBox/...) environments.
"""

I may be misunderstanding your question. But if you are speaking of performance degradation due to excessive timer interrupts when many instances of the kernel are running, I think that the really exciting news on this front lies not with the scheduler, but with the tickless kernel patch, applied to 2.6.21-rc1, and due to be released in a stable kernel possibly as soon as next week.

But the tickless patch itself is only the beginning. Next will follow patches with the batching of interrupts in mind, so that more things get scheduled to be done during one wake up period of the processor (virtual or otherwise), resulting in even fewer interrupts.

edit: Just a few more notes. Tickless in 2.6.21 will be an option, not the default. It is only available on x86 (32 bit), but should be available on other architectures shortly. FC7 will have tickless on by default. My laptop has gone tickless (2.6.21-rc6) and I've had no problems so far.

Edited 2007-04-23 04:03

Reply Parent Score: 5