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Re: [Xen-users] Xen scheduler setup

To: "trilok nuwal" <tc.nuwal@xxxxxxxxx>
Subject: Re: [Xen-users] Xen scheduler setup
From: "Ashish Gupta" <ashishgup@xxxxxxxxx>
Date: Thu, 17 May 2007 17:05:05 -0500
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Also, you said "As from xen documantion, boot time sched=credit or sedf is used to set the scheduler for the xen hosts."
Boot time here refers to boot time of dom0 or boot time of the guests ?


On 5/17/07, Ashish Gupta <ashishgup@xxxxxxxxx> wrote:
Thanks Trilok for the clarification !

On running some of your commands I get the following output. Does this seem to indicate I am running the credit scheduler ? xm dmesg doesn't tell me.

I get the following output:
# xm sched-sedf
Name                              ID Period(ms) Slice(ms) Lat(ms) Extra Weight
Domain-0                          -1      -0.0      -0.0    -0.0     -1     -1
domain1                           -1      -0.0      -0.0    -0.0     -1     -1
domain2                           -1      -0.0      -0.0    -0.0     -1     -1
[root@virtuoso-32 sys]#

# xm sched-credit
Error: No domain given.
Usage: xm sched-credit -d <Domain> [-w[=WEIGHT]|-c[=CAP]]

Get/set credit scheduler parameters.
  -d DOMAIN, --domain=DOMAIN     Domain to modify                          
  -w WEIGHT, --weight=WEIGHT     Weight (int)                              
  -c CAP, --cap=CAP              Cap (int)                                 

# xm sched-credit -d 0
{'cap': 0, 'weight': 256}

On 5/17/07, trilok nuwal <tc.nuwal@xxxxxxxxx > wrote:

I havent tried this, but there are two sheduler credit and sedf scheduler for xen host and this would be common for all the domains. As from xen documantion, boot time sched=credit or sedf is used to set the scheduler for the xen hosts.

For this there are two commands to set and get the parameters of the scheduler for individual domin depednding on the scheduler. Scheduler cant be differnet for the different domains.

#xm  sched-credit
#xm  sched-sedf 

sched-credit         Get/set credit scheduler parameters.
 sched-sedf           Get/set EDF parameters.

# xm sched-credit
Name                              ID Weight Cap
Domain-0                           0    256    0
os218                              7    256    0
# xm sched-sedf
Error: Xen is running with the credit scheduler
# xm sched-sedf --help
Usage: xm sched-sedf <Domain> [options]

Get/set EDF parameters.
  -p [MS], --period[=MS]         Relative deadline(ms)
  -s [MS], --slice[=MS]          Worst-case execution time(ms). (slice <
  -l [MS], --latency[=MS]        Scaled period (ms) when domain performs
                                 heavy I/O
  -e [FLAG], --extra[=FLAG]      Flag (0 or 1) controls if domain can run
                                 in extra time.
  -w [FLOAT], --weight[=FLOAT]   CPU Period/slice (do not set with

# xm sched-credit --help
Usage: xm sched-credit [-d <Domain> [-w[=WEIGHT]|-c[=CAP]]]

Get/set credit scheduler parameters.
  -d DOMAIN, --domain=DOMAIN     Domain to modify
  -w WEIGHT, --weight=WEIGHT     Weight (int)
  -c CAP, --cap=CAP              Cap (int)

I dont think bvt scheduler is available in latest xen 3.0 ( Not sure ).
Hope this will be worthful to you.


On 5/17/07, Ashish Gupta < ashishgup@xxxxxxxxx> wrote:

I have been trying to setup Xen scheduling but have some questions:
1. When do we exactly specify the scheduler to use ? At dom0 boot time (i.e. when the host boots) or when the domU is created with xm ?

2. Can we change the scheduler when a domU is already running ?

3. Can we change the existing scheduler parameters at runtime for domU or dom0 ?

4. How do we figure out which scheduler is currently being used ?

The answers are probably straightforward but I haven't found a tutorial or a guide that explains these points, esp 2,3, or 4.

I am trying to experiment with the bvt scheduler and tried passing sched=bvt at xm create time. But I can't figure out if its actually being used or how to change its parameters.
Any help is greatly appreciated.



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