Re: patch for virtual machine oriented scheduling(1)

[Andrew Theurer <habanero@linux.vnet.ibm.com>]

alex wrote:
> the following patchs provide an extra control(besides the control of
> Linux scheduler) over the execution of vcpu threads.
>
> In this patch, Xen's credit
> scheduler(http://wiki.xensource.com/xenwiki/CreditScheduler) is used.
> User can use  "cat" and
> "echo" command to view and control a guest os' credit.
> e.g.,
> [root@localhost ~]#  echo "weight=500" > /proc/kvm/12345
> will change the credit of guest whose qemu process has the pid 12345 to be 500.
>
> The patch consists of 3 parts:
> 1. modification to the standard KVM
> 2. modification to the Xen scheduler
> 3. helper functions
>   
Just wondering, was it not possible to introduce a new scheduling class 
in the current scheduler?  My impression was that the current scheduler 
was fairly modular and should allow this.

-Andrew


> However, some are unnecessary in the latest Linux kernel.
>
> The difficulties in the ports lie in:
> 1. Linux does not provide timer mechanism that the timer function is
> bind to a dedicate CPU:
>     in case of one cpu receives another cpu's schedule timer
> expiration, IPI is used to relay it.
> 2. before linux 2.6.27, the smp_call_function_xxx()  can not be re-entered.
>    if kvm is sending ipi at the time of relaying timer expiration
> information, deadlock would occur in kernel versions below 2.6.27
>
> In my implementation, tasklets are used to run the function of
> scheduling, and  kernel thread is used to send IPI(in kernels above
> 2.6.27, this is unnecessary)
>
> Originally, this code is developed at the release version of KVM-83.
> In order to post it, I ported to the latest .git tree.  As a result,
> modifications to files like external-module-compat-comm.h are omited.
>
> NOTE:
> 1. Because my not having an AMD machine, only intel platforms are tested.
> 2. Because sched_setaffinity() is used (while Linux does not export
> this symbol), the way of loading kvm modules are changed to be
> ./myins <directory that holds the kvm.ko and kvm-intel.ko>
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