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xen-devel
Re: [Xen-devel] Interrupt levels
I was thinking about it this morning, thinking that interrupts coming
from the MPT control would probably have an affect on disk IO, and thus
a very noticable affect on system performace. Then I realised maybe the
other no standard config item that comes up at boot was a second bridge.
Unfortunately I had to wait until this afternoon so I could get into the
colo, and my DSL link is down at the moment.
nic@stateless:~$ vmstat 3
procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
r b swpd free buff cache si so bi bo in cs us sy id wa
2 0 0 4312 200 85008 0 0 10 13 412 17 0 0 100 0
0 0 0 4312 200 85008 0 0 0 0 196987 14 0 0 100 0
nic@stateless:~$ sudo ifdown internal-br
nic@stateless:~$ vmstat 3
procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
r b swpd free buff cache si so bi bo in cs us sy id wa
2 0 0 4776 200 85012 0 0 10 13 455 17 0 0 100 0
0 0 0 4776 200 85012 0 0 0 51 48 26 0 0 100 0
0 0 0 4776 200 85012 0 0 0 0 40 14 0 0 100 0
The exact problem is 'bridge hello time' being set to zero.
When I when I switch between '0' and '1' hello time via:
auto internal-br
iface internal-br inet static
address 10.8.0.254
netmask 255.255.0.0
network 10.8.0.0
broadcast 10.8.255.255
bridge_ports eth1
bridge_fd 0
bridge_hello 1
bridge_stp off
load switches:
nic@stateless:~$ sudo vi /etc/network/interfaces
[1]+ Stopped sudo vi /etc/network/interfaces
nic@stateless:~$ sudo ifup internal-br
Waiting for internal-br to get ready (MAXWAIT is 2 seconds).
nic@stateless:~$ vmstat 3
procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
r b swpd free buff cache si so bi bo in cs us sy id wa
2 0 0 5504 176 84000 0 0 10 13 0 17 0 0 100 0
0 0 0 5520 176 84000 0 0 0 4 176557 17 0 0 100 0
0 0 0 5520 176 84000 0 0 0 60 171743 28 0 0 100 0
nic@stateless:~$ sudo ifdown internal-br
nic@stateless:~$ fg
[1]+ Stopped sudo vi /etc/network/interfaces
nic@stateless:~$ sudo ifup internal-br
Waiting for internal-br to get ready (MAXWAIT is 2 seconds).
nic@stateless:~$ vmstat 3
procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
r b swpd free buff cache si so bi bo in cs us sy id wa
2 0 0 5504 176 84012 0 0 10 13 43 17 0 0 100 0
0 0 0 5528 176 84012 0 0 0 0 68 13 0 0 100 0
0 0 0 5544 176 84012 0 0 0 13 71 15 0 0 100 0
vmstat with some load on the machine. (Guest running mutt loading folder
via imap/nfs.)
nic@stateless:~/sys/xen$ vmstat 3
procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
r b swpd free buff cache si so bi bo in cs us sy id wa
2 0 0 9088 208 84740 0 0 12 14 43 18 0 0 100 0
0 0 0 9088 208 84740 0 0 527 47 949 403 0 0 100 0
0 0 0 9096 208 84740 0 0 561 1 913 408 0 1 99 0
0 0 0 9096 208 84740 0 0 536 15 982 402 0 1 99 0
0 0 0 9104 208 84740 0 0 659 37 941 309 0 3 97 0
0 0 0 9040 208 84740 0 0 2679 68 2163 412 0 3 97 0
0 0 0 9040 208 84740 0 0 2751 5 2178 403 0 2 98 0
0 0 0 8912 208 84740 0 0 3020 31 2389 387 0 3 97 0
0 0 0 8912 208 84740 0 0 3592 43 3125 906 0 1 99 0
0 0 0 8912 208 84740 0 0 2427 201 1909 356 0 3 97 0
0 0 0 8912 208 84740 0 0 1157 89 1279 327 0 4 96 0
0 0 0 8912 208 84740 0 0 124 497 415 128 0 3 97 0
0 0 0 8912 208 84740 0 0 0 605 542 244 0 7 93 0
0 0 0 8912 208 84740 0 0 0 82 415 114 0 3 97 0
0 0 0 8912 208 84740 0 0 0 395 2596 43 0 19 81 0
Idle:
nic@stateless:~$ vmstat 3
procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
r b swpd free buff cache si so bi bo in cs us sy id wa
0 0 0 7832 208 84748 0 0 13 14 45 18 0 0 100 0
0 0 0 7832 208 84748 0 0 0 12 68 24 0 0 100 0
0 0 0 7840 208 84748 0 0 0 3 61 15 0 0 100 0
0 0 0 7840 208 84748 0 0 0 0 64 12 0 0 100 0
For completeness:
nic@stateless:~$ dmesg | grep eth1
eth1: Tigon3 [partno(BCM95703A30) rev 1002 PHY(5703)] (PCIX:100MHz:64-bit)
10/100/1000BaseT Ethernet 00:0d:60:d5:66:6d
eth1: RXcsums[1] LinkChgREG[0] MIirq[0] ASF[0] Split[0] WireSpeed[1] TSOcap[1]
device eth1 entered promiscuous mode
device eth1 left promiscuous mode
internal-br: port 1(eth1) entering disabled state
device eth1 entered promiscuous mode
Note, I used a hello time of 0 with UML on a standard host kernel. [1]
Although I never noticed this level of interrupts previously.
xen-br0 seems to default to non-zero hello time:
nic@stateless:/proc/sys$ sudo brctl showstp xen-br0
xen-br0
bridge id 8000.000d60d5666c
designated root 8000.000d60d5666c
root port 0 path cost 0
max age 20.00 bridge max age 20.00
hello time 2.00 bridge hello time 2.00
forward delay 0.00 bridge forward delay 0.00
ageing time 300.00
hello timer 1.22 tcn timer 0.00
topology change timer 0.00 gc timer 62.60
flags
internal-br0 with hello set to 1 is:
nic@stateless:/proc/sys$ sudo brctl showstp internal-br
internal-br
bridge id 8000.000d60d5666d
designated root 8000.000d60d5666d
root port 0 path cost 0
max age 20.00 bridge max age 20.00
hello time 1.00 bridge hello time 1.00
forward delay 0.00 bridge forward delay 0.00
ageing time 300.00
hello timer 0.44 tcn timer 0.00
topology change timer 0.00 gc timer 36.98
flags
After discovered, I figrued it wasn't worth trying the LiveCD.
[1] Settings I've used for UML come from
http://edeca.net/articles/bridging/create-bridge.html
Nicholas
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