Hi so I ran these tests again. No patch applied yet. And - at least once - it worked. I did everything exactly the same way as before. Since the logs are 8 MB, even when best-bzip2'd, and I don't want everybody to have to download these, I uploaded them to an external hoster: http://www.megaupload.com/?d=SWKTC0V4 Traces were created with blktrace -n 64 -b 16384 -d /dev/sdb -o - | blkparse -i - blktrace -n 64 -b 16384 -d /dev/vdisks/kernel3 -o - | blkparse -i -
Can you please apply attached patch.
Unfortunately not. Cannot be applied to 2.6.37. I guess your source is newer and I fail to find the places in the file to patch manually.
This just makes CFQ output little more verbose and run the test again and capture the trace.
- Start the trace on /dev/sdb - Start the dd jobs in virt machines - Wait for system to hang - Press CTRL-C - Make sure there were no lost events otherwise increase the size and number of buffers.
Tried that. Unfortunately, even with max buffer size of 16 M [1], this leaves some Skips. I also tried to increase the number of buffers over 64, but that produced Oops'es. However, I attached kernel3's blktrace of a case where the error occured. Maybe you can read something from that.
Can you also open tracing in another window and also trace one of the throttled dm deivces, say /dev/disks/kernel3. Following the same procedure as above. So let the two traces run in parallel.
So what next? Regards Dominik [1] http://git.kernel.org/?p=linux/kernel/git/axboe/blktrace.git;a=blob_plain;f=... and look for "Invalid buffer"