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Re: Bad performance with Xen
Hi guys. Maybe we are suffering some related issue.
If not, feel free to ignore this message.
I wrote on this list but none replyed:
"Fresh installed server
with Debian Buster on top of nvme swRaid1 (mdadm)
Testing hdd write seed with dd (with convert=fdatasync option)
gives me the result of 330MB/s. Good.
Installed xen-system and xen-tools (with --no-recommends option
in apt) from official repository. Rebooted the system.
Re-tested hdd write seed
with dd (with convert=fdatasync option) gives me the result of
108MB/s. Not good at all.
Maybe the following is not related to the issue, but on dmesg
there is a line when I boot the system with Xen kernel:
...
[ 14.214044] Performance Events: unsupported p6 CPU model
158 no PMU driver, software events only.
...
Instead, when I boot the system without Xen kernel I have
these lines in dmesg:
...
[ 0.517217] Performance Events: PEBS fmt3+, Skylake events,
32-deep LBR, full-width counters, Intel PMU driver.
[ 0.517356] ... version: 4
[ 0.517444] ... bit width: 48
[ 0.517444] ... generic registers: 4
[ 0.517444] ... value mask: 0000ffffffffffff
[ 0.517444] ... max period: 00007fffffffffff
[ 0.517444] ... fixed-purpose events: 3
[ 0.517444] ... event mask: 000000070000000f
"
Personally, I moved to KVM+libvirt nearly without rework.
I/O performance are great.
But I love XEN and I will be pleased to come back to it.
g
On 03/05/20 19:24, Agustin Lopez wrote:
Sorry. I booted with 8 GB for the Dom0 and all is the same.
I have seen one difference between the 2 xl info:
(AGUSTIN) virt_caps : hvm hvm_directio
(OLIVIER) virt_caps : pv hvm hvm_directio
pv_directio hap shadow iommu_hap_pt_share
Could this be the problem?
Agustín
El 3/5/20 a las 18:50, Rob Townley
escribió:
Agustin, noticed ‘ dom0_mem=2048M,max:4065M’,
so increasing RAM
allocated to Dom0 might speed up the VMs.
2GB for dom0 is extremely low in
my opinion especially when most of the 256GB of host RAM
is going to waste.
dom0_mem=2048M,max:4065M
Hard to tell. Here is my xl info to compare:
host : xcp-ng-lab-3
release : 4.19.0+1
version : #1 SMP Thu Feb 13 17:34:28
CET 2020
machine : x86_64
nr_cpus : 4
max_cpu_id : 3
nr_nodes : 1
cores_per_socket : 4
threads_per_core : 1
cpu_mhz : 3312.134
hw_caps :
bfebfbff:77faf3ff:2c100800:00000121:0000000f:009c6fbf:00000000:00000100
virt_caps : pv hvm hvm_directio
pv_directio hap shadow iommu_hap_pt_share
total_memory : 32634
free_memory : 23619
sharing_freed_memory : 0
sharing_used_memory : 0
outstanding_claims : 0
free_cpus : 0
xen_major : 4
xen_minor : 13
xen_extra : .0-8.4.xcpng8.1
xen_version : 4.13.0-8.4.xcpng8.1
xen_caps : xen-3.0-x86_64
xen-3.0-x86_32p hvm-3.0-x86_32 hvm-3.0-x86_32p
hvm-3.0-x86_64
xen_scheduler : credit
xen_pagesize : 4096
platform_params : virt_start=0xffff800000000000
xen_changeset : 85e1424de2dd, pq f9dbf852550e
xen_commandline : watchdog ucode=scan
dom0_max_vcpus=1-4 crashkernel=256M,below=4G
console=vga vga=mode-0x0311 dom0_mem=8192M,max:8192M
cc_compiler : gcc (GCC) 4.8.5 20150623 (Red
Hat 4.8.5-28)
cc_compile_by : mockbuild
cc_compile_domain : [unknown]
cc_compile_date : Tue Apr 14 18:28:14 CEST 2020
build_id :
5ad6f12499d7f264544b64568b378260cd82a65f
xend_config_format : 4
I'm on XCP-ng 8.1. Other diff is also I have more
GHz than you. So I ran the test on another server
(building a VM just for you :p ) and here is the
result for a Xeon E5-2650L v2 @ 1.70GHz (slow!) and VM
disk stored on a NFS share.
real 0m5,925s
user 0m3,769s
sys 0m2,321s
Still, far better than 20 seconds you have!
Let me know if you need further help :)
Best,
Olivier.
Hi Oliver.
I am testing a bit more. In seconds, the results of
the command is:
Debian Buster PV -> 18'
Debian Buster HVM -> 8'
Debian Buster PVHVM -> 8'
Debian Buster PVH -> 8'
xl info
release : 4.19.0-8-amd64
version : #1 SMP Debian
4.19.98-1+deb10u1 (2020-04-27)
machine : x86_64
nr_cpus : 48
max_cpu_id : 47
nr_nodes : 2
cores_per_socket : 12
threads_per_core : 2
cpu_mhz : 2197.458
hw_caps :
bfebfbff:77fef3ff:2c100800:00000121:00000001:001cbfbb:00000000:00000100
virt_caps : hvm hvm_directio
total_memory : 261890
free_memory : 255453
sharing_freed_memory : 0
sharing_used_memory : 0
outstanding_claims : 0
free_cpus : 0
xen_major : 4
xen_minor : 11
xen_extra : .4-pre
xen_version : 4.11.4-pre
xen_caps : xen-3.0-x86_64
xen-3.0-x86_32p hvm-3.0-x86_32 hvm-3.0-x86_32p
hvm-3.0-x86_64
xen_scheduler : credit
xen_pagesize : 4096
platform_params :
virt_start=0xffff800000000000
xen_changeset :
xen_commandline : placeholder
dom0_mem=2048M,max:4065M
cc_compiler : gcc (Debian 8.3.0-6) 8.3.0
cc_compile_by : pkg-xen-devel
cc_compile_domain : lists.alioth.debian.org
cc_compile_date : Wed Jan 8 20:16:51 UTC
2020
build_id :
b6822aa1d8f867753b92985e5cb0e806e520a08c
xend_config_format : 4
Oliver, I got > double values than you. Where
is the problem?
Regards,
Agustín
El 2/5/20 a las 19:56, Olivier Lambert escribió:
Hi Agustin,
I just did a test on XCP-ng 8.1 (Xen 4.13)
with a fresh Debian 10 VM, and here is the
result I have:
```
# time for i in `dpkg -L ncurses-term |
sort`; do if [ -f "$i" ]; then ls -ld "$i";
fi; done | tr -s " "| cut -d" " -f5,9
>/dev/null
real 0m2,741s
user 0m2,248s
sys 0m0,574s
```
My hardware isn't ultra modern: Xeon(R) CPU
E3-1225 v5 (3.3Ghz) on a small Dell T30
machine, VM storage on local HDD. I did the
test 3 times, and I have always results
between 2,6 and 2,8 secs.
Regards,
Olivier.
Hello.
We are testing low performance in IO with the
next command in Debian Buster (kernel
4.19.0-8-amd64) with Xen (4.11.4-pre)
time for i in `dpkg -L ncurses-term |
sort`; do if [ -f "$i" ]; then ls -ld "$i";
fi; done | tr -s " "| cut -d" " -f5,9
>/dev/null
In all our Dom0s - DomUs we are getting
around 20 seconds.
In the same physical machines booting with
Debian without Xen, we get 5-7 seconds
In some KVM VMs in other server we are geting
almost the same as physical.
(all in local Disks. XFS filesystems. Images
of DomUs in raw format)
I have booted Xen with 4.8 y 4.4 releases with
almost the same bad data.
Where could be the problem?
I think of is not normal this difference
between DomUs and physical machine.
Every pointer will be welcomed.
Best regards,
Agustín
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