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 ^ ?
Thank you,
Adrian
Todd Deshane wrote:
>
>
> On Tue, Jul 8, 2008 at 6:54 AM, Adrian Turcu <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
>
>
> _______________________________________________
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>
>
>
>
> --
> Todd Deshane
> http://todddeshane.net
> check out our book: http://runningxen.com
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