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Re: [Xen-users] How To Pin domU VCPU To Specific CPU During Instance Cre

To: deshantm@xxxxxxxxx
Subject: Re: [Xen-users] How To Pin domU VCPU To Specific CPU During Instance Creation
From: Adrian Turcu <adriant@xxxxxxxxxx>
Date: Tue, 08 Jul 2008 15:58:12 +0100
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No problem. I'll give it some more time here and then follow-up with the devel 
list.

Thank you,
Adrian

Todd Deshane wrote:
> 
> 
> On Tue, Jul 8, 2008 at 10:47 AM, Adrian Turcu <adriant@xxxxxxxxxx
> <mailto:adriant@xxxxxxxxxx>> wrote:
> 
>     Thanks for the quick reply Todd, but I guess my problem is not to
>     exclude certain CPUs to be used by the guests,
>     but to pin down VCPUs to specific CPUs when using a list.
>     Take this one for example on my config:
> 
>     ### shared-smq6
>     cpus = "1,2"
>     vcpus = 2
> 
>     That means, I use a circular list of CPU 1 and CPU 2, and 2 VCPUs
>     which can pick any from the list.
>     This is true as per output of "xm vcpu-list shared-smq6" command:
> 
>     Name                              ID  VCPU   CPU State   Time(s) CPU
>     Affinity
>     shared-smq6                        5     0     1   -b-   21713.0 1-2
>     shared-smq6                        5     1     1   -b-   31214.3 1-2
> 
>     What I would like is to be able to say in the config file directly,
>     i.e. "use CPU 1 for VCPU 0 and CPU 2 for VCPU 1"
>     At the moment I can do that only by using "xm vcpu-pin" command.
> 
>     If that is already in those threads, I cannot see it to be honest.
>     Could you just sent the kind of config you envisage by using ^ ?
> 
> 
> I actually don't have a lot of personal experience with vcpu pinning.
> 
> That thread I gave you was the first time I saw the syntax for it.
> 
> Any thoughts or experiences from others?
> 
> If after a day or two on the users list and no response/no solutions.
> Feel free to post a fresh post to xen-devel with all the details of what
> you have tried, what works etc.
> 
> If it was me, I would try to read through the source code to find the
> answer. I can't commit to helping you with that today due to time
> constraints.
> 
> Good luck.
> 
> Best Regards,
> Todd
>  
> 
> 
>     Thank you,
>     Adrian
> 
> 
>     Todd Deshane wrote:
>     >
>     >
>     > On Tue, Jul 8, 2008 at 6:54 AM, Adrian Turcu <adriant@xxxxxxxxxx
>     <mailto:adriant@xxxxxxxxxx>
>     > <mailto:adriant@xxxxxxxxxx <mailto:adriant@xxxxxxxxxx>>> wrote:
>     >
>     >     Hi all
>     >
>     >     I was browsing the archives to find a solution to my "problem" but
>     >     with no luck.
>     >     Here is the scenario:
>     >
>     >     Host:
>     >     Hardware: Dell PE 1950, 4 x dual core CPU, 16GB RAM
>     >     OS: FC8, kernel 2.6.21-2950.fc8xen
>     >     Xen version: 3.1.0-rc7-2950.fc8
>     >
>     >     Guests:
>     >     OS: FC8, kernel 2.6.21-2950.fc8xen
>     >
>     >     I want to be able during guest instance creation to pin down
>     each of
>     >     the VCPUs to specific CPU cores.
>     >     I can do that after the instance is up by using "xm vcpu-pin"
>     >     command, but I would love to be able to do it straight from the
>     >     config file.
>     >
>     >
>     >
>     > I would suggest this thread:
>     >
>     
> http://markmail.org/search/?q=xen-devel+ian+pratt+cpu+pin+syntax#query:xen-devel%20ian%20pratt%20cpu%20pin%20syntax+page:1+mid:2vlhnty3zemednba+state:results
>     >
>     > Take a look at the syntax with the ^
>     >
>     > Hope that helps,
>     > Todd
>     >
>     >
>     >
>     >
>     >     two config files:
>     >
>     >     ### shared-db4
>     >     kernel = "/boot/vmlinuz-2.6.21-2950.fc8xen"
>     >     ramdisk = "/boot/initrd-2.6.21-2950.fc8xen-domU.img"
>     >     name = "shared-db4"
>     >     memory = 8192
>     >     cpus = "4,5"
>     >     vcpus = 2
>     >     vif = [ 'mac=00:16:3E:13:02:01, bridge=br162',
>     >     'mac=00:16:3E:13:04:01, bridge=br164' ]
>     >     disk = [
>     >    
>     
> 'phy:disk/by-path/ip-nas01-681:3260-iscsi-iqn.2008-02.com.newbay.celerra.domu-root-lun-0-part1,hda1,r'
>     >     ,
>     >    
>     
> 'phy:disk/by-path/ip-nas01-681:3260-iscsi-iqn.2008-02.com.newbay.celerra.domu-00163e130001-lun-0-part1,hdb1,w'
>     >     ,
>     >    
>     
> 'phy:disk/by-path/ip-nas01-681:3260-iscsi-iqn.2008-02.com.newbay.celerra.domu-00163e130001-lun-1-part1,hdc1,w'
>     >     ,
>     >    
>     
> 'phy:disk/by-path/ip-nas01-681:3260-iscsi-iqn.2008-02.com.newbay.celerra.domu-00163e130001-lun-2-part1,hdd1,w'
>     >     ]
>     >     root = "/dev/hda1 ro"
>     >     extra = "3 selinux=0 enforcing=0"
>     >     on_poweroff = 'destroy'
>     >     on_reboot   = 'restart'
>     >     on_crash    = 'restart'
>     >
>     >
>     >
>     >     ### shared-smq6
>     >     kernel = "/boot/vmlinuz-2.6.21-2950.fc8xen"
>     >     ramdisk = "/boot/initrd-2.6.21-2950.fc8xen-domU.img"
>     >     name = "shared-smq6"
>     >     memory = 2560
>     >     cpus = "1,2"
>     >     vcpus = 2
>     >     vif = [ 'mac=00:16:3E:13:03:03, bridge=br163' ]
>     >     disk = [
>     >    
>     
> 'phy:disk/by-path/ip-nas01-681:3260-iscsi-iqn.2008-02.com.newbay.celerra.domu-root-lun-0-part1,hda1,r'
>     >     ,
>     >    
>     
> 'phy:disk/by-path/ip-nas01-681:3260-iscsi-iqn.2008-02.com.newbay.celerra.domu-00163e130003-lun-0-part1,hdb1,w'
>     >     ,
>     >    
>     
> 'phy:disk/by-path/ip-nas01-681:3260-iscsi-iqn.2008-02.com.newbay.celerra.domu-00163e130003-lun-1-part1,hdc1,w'
>     >     ,
>     >    
>     
> 'phy:disk/by-path/ip-nas01-681:3260-iscsi-iqn.2008-02.com.newbay.celerra.domu-00163e130003-lun-2-part1,hdd1,w'
>     >     ]
>     >     root = "/dev/hda1 ro"
>     >     extra = "3 selinux=0 enforcing=0"
>     >     on_poweroff = 'destroy'
>     >     on_reboot   = 'restart'
>     >     on_crash    = 'restart'
>     >
>     >
>     >     "xm vcpu-list" output:
>     >     Name                              ID  VCPU   CPU State  
>     Time(s) CPU
>     >     Affinity
>     >     Domain-0                           0     0     0   r--
>      118567.5 any cpu
>     >     Domain-0                           0     1     -   --p      
>     2.9 any cpu
>     >     Domain-0                           0     2     -   --p    
>      30.4 any cpu
>     >     Domain-0                           0     3     -   --p      
>     2.2 any cpu
>     >     Domain-0                           0     4     -   --p      
>     3.2 any cpu
>     >     Domain-0                           0     5     -   --p      
>     2.0 any cpu
>     >     Domain-0                           0     6     -   --p      
>     2.0 any cpu
>     >     Domain-0                           0     7     -   --p      
>     3.8 any cpu
>     >     shared-db4                         6     0     4   r--  446383.3 4
>     >     shared-db4                         6     1     5   -b-   89830.3 5
>     >     shared-smq4                        2     0     6   -b-  
>     53710.6 6-7
>     >     shared-smq4                        2     1     6   -b-  
>     87263.8 6-7
>     >     shared-smq6                        5     0     1   -b-  
>     21681.7 1-2
>     >     shared-smq6                        5     1     1   -b-  
>     31198.6 1-2
>     >
>     >     shared-db4 was altered after instance creation by using "xm
>     vcpu-pin
>     >     shared-db4 0 4 ; xm vcpu-pin shared-db4 1 5",
>     >     the rest of the guests are as they were created using "xm create
>     >     <config file>" command or automatically started at host reboot
>     >     (/etc/xen/auto folder).
>     >
>     >     Don't know if this has an impact or not, but I am using sedf
>     >     scheduler and I have a cron job which sets weight=1 for all newly
>     >     created instances:
>     >     #!/bin/bash
>     >
>     >     # change weigth to 1
>     >     /usr/sbin/xm sched-sedf | grep -v Name | tr -s ' ' | cut -d\
>      -f7,1
>     >     | while read a b ; do if [ $b -eq 0 ] ; then /usr/sbin/xm
>     sched-sedf
>     >     $a -w1 ; fi ; done
>     >
>     >
>     >     The reason:
>     >
>     >     I can see in the guest domains a lot of percentage spent in "CPU
>     >     Steal" column
>     >     when the systems are under heavy CPU pressure.
>     >     Changing the CPU affinity on each VCPU seem to keep "CPU steal" in
>     >     the guests to almost 0 during similar system loads.
>     >
>     >     I also came across this old article (maybe still valid):
>     >
>     >     http://virt.kernelnewbies.org/ParavirtBenefits
>     >
>     >     which in particular states:
>     >
>     >     "The time spent waiting for a physical CPU is never billed
>     against a
>     >     process,
>     >     allowing for accurate performance measurement even when there
>     is CPU
>     >     time contention between *multiple virtual machines*.
>     >
>     >     The amount of time the virtual machine slowed down due to such CPU
>     >     time contention is split out as so-called "steal time"
>     >     in /proc/stat and properly displayed in tools like vmstat(1),
>     top(1)
>     >     and sar(1)."
>     >
>     >     Is this because the CPU affinity is shared with Domain-0?
>     >     Maybe I am mixing stuff here, nevertheless, I'd like to be able to
>     >     pin each VCPU to a physical CPU core (if that makes sense).
>     >
>     >
>     >     Thank you in advance,
>     >     Adrian
>     >
>     >
>     >     _______________________________________________
>     >     Xen-users mailing list
>     >     Xen-users@xxxxxxxxxxxxxxxxxxx
>     <mailto:Xen-users@xxxxxxxxxxxxxxxxxxx>
>     <mailto:Xen-users@xxxxxxxxxxxxxxxxxxx
>     <mailto:Xen-users@xxxxxxxxxxxxxxxxxxx>>
>     >     http://lists.xensource.com/xen-users
>     >
>     >
>     >
>     >
>     > --
>     > Todd Deshane
>     > http://todddeshane.net
>     > check out our book: http://runningxen.com
> 
> 
> 
> 
> 
> -- 
> Todd Deshane
> http://todddeshane.net
> check out our book: http://runningxen.com




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