Description of problem: Using the new 2.6.22.1-15 kernel makes my machine very slow. Using hdparm, I discovered the speed ~1.6 MB/sec vs ~49MB/sec with 2.6.20. Version-Release number of selected component (if applicable): kernel-2.6.22.1-15 Dell M65 How reproducible: Happens every time I boot the 2.6.22.1-15 kernel. Steps to Reproduce: 1.Boot System Actual results: Under kernel 2.6.22.1-15 using: hdparm -tT /dev/hda /dev/hda: Timing cached reads: 11792 MB in 1.99 seconds = 5916.75 MB/sec Timing buffered disk reads: 6 MB in 3.54 seconds = 1.69 MB/sec Expected results: Under kernel 2.6.20-1.2962.fc6 using hdparm -tT /dev/sda /dev/sda: Timing cached reads: 14492 MB in 1.99 seconds = 7273.03 MB/sec Timing buffered disk reads: 148 MB in 3.00 seconds = 49.27 MB/sec Additional info: I've tried the 2.6.22 kernel with nohz=off highres=off, which doesn't make a difference. I'm attaching the output of hdparm -tT /dev/xda, lsmod, and dmesg for both kernels. Here's the email to the test list where I reported the problem: https://www.redhat.com/archives/fedora-test-list/2007-July/msg00372.html
Created attachment 159566 [details] output of hdparm, lsmod, dmesg for 6.20 and 6.22.1-15
This is really strange. In the FC6 2.6.20 kernels, the IDE driver does not claim the drive; later on ata_piix gets control: Uniform Multi-Platform E-IDE driver Revision: 7.00alpha2 ide: Assuming 33MHz system bus speed for PIO modes; override with idebus=xx ide0: I/O resource 0x1F0-0x1F7 not free. ide0: ports already in use, skipping probe In 2.6.22, IDE does: Uniform Multi-Platform E-IDE driver Revision: 7.00alpha2 ide: Assuming 33MHz system bus speed for PIO modes; override with idebus=xx Probing IDE interface ide0... Clocksource tsc unstable (delta = -101028827 ns) hda: Hitachi HTS721010G9SA00, ATA DISK drive So what changed? The configuration looks the same, with IDE built in and the ata driver as a module.
2.6.22 no longer includes the rather horrible combined mode hacks to allow split driver support so you must use libata for both in those cases. With old IDE loaded and libata modular old IDE will claim the device as a legacy device and stop libata claiming it
This should be fixed an all recent FC6 2.6.22 kernels. (The combined_mode code was backported.)