RE: [Xen-users] domains gets stalled for N seconds - problem with DMA?

[<damjan.pipan.list@xxxxxxx>]

Hi,

I still have problems with io performance. Please tell me if I am doing 
something wrong. It seams that Xen can not run two domains
with a lot of IO usage - a lot of requests not transfer?

Tests:

I have 8 SAS drives and 8 SATA drives. I have created:
- 7 SAS in RAID6 and installed dom0 on this volume group
- 7 SATA in RAID6 and installed domain-1 on this volume group
- 1 SAS as volume and installed domain-2 on this volume group

I have set the scheduler credits
- dom0 - 60000
- dom1 - 1
- dom2 - 1

1 case:
=====
dom1 - write few hundreds of files per minute.
dom2 - idle

IT WORKS NORMALLY - few percent of wait/user in dom1

2 case:
=====
- dom2: tar xfz file.tgz with 3 milion of small files (1 KB)

The domain 1 in this case get from 30-100% wait time. 

IMPORTANT:
- dom1 and dom2 are on different arrays.
- I run also top -d .5 on dom0 ---> it is usually idle but sometimes process 
blkback.17.sda1 gets to the top just for a moment (17
is ID of dom-2)
- I checked also xm top and dom1 is 0 CPU usage when top in dom1 shows 100 wait 
time 

----
Hardware/software is 
2 * Intel(R) Xeon(R) CPU           E5450  @ 3.00GHz
Adaptec 31605 controller

uname -a:
Linux xen-de 2.6.18.8-xen #2 SMP Fri Jun 27 21:27:02 UTC 2008 x86_64 GNU/Linux

host                   : xen-de
release                : 2.6.18.8-xen
version                : #2 SMP Fri Jun 27 21:27:02 UTC 2008
machine                : x86_64
nr_cpus                : 8
nr_nodes               : 1
cores_per_socket       : 4
threads_per_core       : 1
cpu_mhz                : 3000
hw_caps                : 
bfebfbff:20100800:00000000:00000140:000ce3bd:00000000:00000001
total_memory           : 16382
free_memory            : 1028
node_to_cpu            : node0:0-7
xen_major              : 3
xen_minor              : 2
xen_extra              : .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          : unavailable
cc_compiler            : gcc version 4.1.2 20061115 (prerelease) (Debian 
4.1.1-21)
cc_compile_by          : root
cc_compile_domain      : xlab.si
cc_compile_date        : Fri Jun 27 23:35:01 CEST 2008
xend_config_format     : 4





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