Red Hat Bugzilla – Bug 122859
slow /md0 raid 5 under smp kernel (ok single, ok smp acpi=off amp=off)
Last modified: 2007-11-30 17:10:42 EST
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Description of problem:
Hardware is Pentium 4 HT capable 2.8Ghz on Abit IC7 Max3 motherboard.
(which is intel 875 chipset) with 1gig of ram.
If I boot the smp kernel then hdparm and normal file access to files
on /dev/md0 mounted as /raid. Raid is 6 200gig sata drives in raid 5
128k chunk filesystem is ext3 block size is 2048 stride is set to 64.
(created with mdadm and started with it)
Using default kernels on fc2 test3 release 2.6.5-1.327 and 2.6.5-1.327smp.
hdparm -Tt /dev/md0 under smp - is 15-22 megabytes/sec
hdparm -Tt /dev/md0 under single cpu - is over 100 megabytes/sec
Reading a 3 gigabyte file from /raid shows an equivalent different in
performance under the smp and single kernels.
hdparm any of the 6 raw drives in the md0 raid.
hdparm -Tt /dev/sda1 - gives around 48 megabytes sec in either the
smp or the single cpu kernel. It appears just the software raid device
is having some sort of problem.
I cannot find any errors appearing in the logs (though maybe i just
dont know all the places to look).
If I boot the smp kernel with acpi=off and apm=off then smp kernel
appears to give same sort of performance as single cpu.
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. boot smp kernel
2. hdparm -Tt /dev/md0
Actual Results: Its much slower in performance than in single cpu
kernel or with acpi=off apm=off.
Please attach the dmesg and /proc/interrupts from the
successful UP kernel, and failing MP kernel.
It may be an IOAPIC issue, since that comes along with the SMP kernel.
Closing this bug due to inactivity.