> On Thu, 7 Dec 2006 14:28:44 +0100 Hartmut Manz <manz@xxxxxxxx> wrote: > I am using here 2 machines with the ICP Vortex SCSI-Controler SCRU32 for some > years now. > > After switching one machine from Debian 3.1 (sarge, with Kernel 2.6.8) to the > upcoming Debian 4.0 (etch with Kernel 2.6.17 or 2.6.18) I have noticed that > my scsi-devices become very slow while there is also a dramatical increase in > the sys time needed for I/O operations. > > The machine is a dual processor Xeon system (2 * 2.2 GHz) with 2 GB memory. > The used scsi drives are seagate R10k and R15k disks. > > i.e. reading 1 GB from the first SCSI drive takes about: > xen-1:/var/log# time dd if=/dev/sda bs=256k count=4000 of=/dev/null > 4000+0 records in > 4000+0 records out > 1048576000 bytes (1.0 GB) copied, 55.3079 seconds, 19.0 MB/s > > real 0m55.361s > user 0m0.368s > sys 0m49.107s ouch. > There are two strange things: > 1. The transfer rate is only 19 MB/sec what is very low for this machine. > The expected value would be at least 50 MB/sec. > > 2. the system time is in the same range as the real time and thats > realy annoying, on the old kernel the system time for such an operatin > was about 7 sec. > It would help a lot of we can determine where the kernel is spending all this time. Can you please generate a kernel profile? Start a large IO operation then, while it is running, run #!/bin/sh sudo opcontrol --stop sudo opcontrol --shutdown sudo rm -rf /var/lib/oprofile sudo opcontrol --vmlinux=/boot/vmlinux-$(uname -r) sudo opcontrol --start-daemon sudo opcontrol --start sleep 10 sudo opcontrol --stop sudo opcontrol --shutdown sudo opreport -l /boot/vmlinux-$(uname -r) | head -50 (might need some adjustments for distro variation) Thanks. - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
