Thorsten von Eicken
2006-Jun-11 23:31 UTC
Re: [Fedora-xen] slow disk performance in Xen0 FC5
> On Wed, 2006-05-31 at 23:07 -0700, Ashe Canvar wrote: > >> For instance my avg data read rate ( tested using hdparm -t /dev/hda) >> is 55MB/s using the regular smp kernel but it falls to 2.6MB/s when I >> boot into dom0. No other domains are runnign at this point. I have >> looked for incrementing interrupts in ide0 , there are none. > > There were some important fixes to Xen''s irq delivery mechanism that > have been added to FC5 since the 1.2080 kernel you are running. Could > you please try updating to a newer kernel and seeing if you can > reproduce the problem?Same problem here. Machine is dog slow whenever disk accesses are required. Running yum takes ages. This is a dual-cpu 2.4Ghz xeon w/ATA drive. Running a stock FC5 kernel I get ~30MB/sec read or write bandwidth. With xen kernel I get 3-7MB/s in dom0 and it varies a lot. Typically I see the following in top (this was taken while running yum): [root@medusa1 ~]# top top - 16:19:22 up 11 min, 2 users, load average: 0.69, 1.63, 1.43 Tasks: 72 total, 1 running, 71 sleeping, 0 stopped, 0 zombie Cpu(s): 7.4% us, 1.5% sy, 0.0% ni, 16.9% id, 0.0% wa, 74.2% hi, 0.0% si Mem: 262308k total, 142696k used, 119612k free, 9072k buffers Swap: 1052248k total, 0k used, 1052248k free, 49168k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 2748 root 15 0 52860 42m 5268 S 49.9 16.5 0:48.33 yum 2778 root 17 0 2140 1004 808 R 10.2 0.4 0:01.75 top 368 root 16 0 0 0 0 S 0.6 0.0 0:04.00 kjournald Note the high %hi! At almost the same time: [root@medusa1 ~]# iostat -x 10 Linux 2.6.16-1.2122_FC5xen0 (medusa1) 06/11/2006 avg-cpu: %user %nice %system %iowait %idle 1.02 0.00 64.62 0.00 34.36 Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s rkB/s wkB/s avgrq-sz avgqu-sz await svctm %util hda 0.00 3.68 0.00 0.72 0.00 35.17 0.00 17.59 49.14 0.00 0.00 0.00 0.00 Almost no disk activity, but high system time. I''m pretty sure it was not doing network I/O. [root@medusa1 ~]# dmesg | head Linux version 2.6.16-1.2122_FC5xen0 (bhcompile@hs20-bc1-3.build.redhat.com) (gcc version 4.1.0 20060304 (Red Hat 4.1.0-3)) #1 SMP Sun May 21 15:34:43 EDT 2006 [root@medusa1 ~]# dmesg | egrep ATA hda: ST380011A, ATA DISK drive [root@medusa1 ~]# dmesg | egrep IDE PCI: Ignoring BAR0-3 of IDE controller 0000:00:1f.1 Uniform Multi-Platform E-IDE driver Revision: 7.00alpha2 ICH3: IDE controller at PCI slot 0000:00:1f.1 Well, the bottom line is that the machine is not usable like this. Grrr. Thorsten