Hi Tomoki, I offline the cpu2 and cpu3 on my machine and continue to try your patch. I run the vm without pass-through device for I only want to know the interrupt latency improvement.(Am I right?) my qemu parameter: ./x86_64-softmmu/qemu-system-x86_64 -enable-kvm -m 1024 -cpu qemu64,+x2apic -no-kvm-pit -serial pty -nographic -drive file=/mnt/sdb/vms/testfc/testfc.qcow2,if=virtio,index=0,format=qcow2 -spice port=12000,addr=186.100.8.171,disable-ticketing,plaintext-channel=main,plaintext-channel=playback,plaintext-channel=record,image-compression=auto_glz -no-kvm-pit cyclictest: cyclictest -m -p 99 -n -l 100000 -h 3000 -q but I got very bad result: avg lantency: 20000+ us max lantency: 50000+ us and got Message from syslogd@kvmsteven at Apr 7 05:43:30 ... kernel:[ 2201.151817] BUG: soft lockup - CPU#18 stuck for 22s! [qemu-system-x86:2365] my setup: host kernel: 3.6.0-rc4+ and your patches guest kernel: 3.6.11.1-rt32 qemu: qemu-kvm-1.0 with your patch BTW, I am sure that my rt-kernel works well, which got 12us max latency as a host OS. Could you please provoide me more detail about your benchmark so I could reproduce your benchmark result? Thanks, Steven ________________________________________ From: Tomoki Sekiyama [tomoki.sekiyama.qu@xxxxxxxxxxx] Sent: Wednesday, April 03, 2013 10:02 To: Yangminqiang Cc: tomoki.sekiyama@xxxxxxx; kvm@xxxxxxxxxxxxxxx Subject: Re: KVM: kvm_set_slave_cpu: Invalid argument when trying direct interrupt delivery Hi, Thank you for testing the patch. Yangminqiang <yangminqiang@xxxxxxxxxx> wrote: > Hi Tomoki > > I tried your smart patch "cpu isolation and direct interrupt delivery", > http://article.gmane.org/gmane.linux.kernel/1353803 > > got output when I run qemu > kvm_set_slave_cpu: Invalid argument > > So I wonder > * Did I misuse your patches? > * How is the offlined CPU assigned? or the Guest OS will automaticly detect > and use it? Currently it is hard-coded in the patch for qemu-kvm just for testing: diff -Narup a/qemu-kvm-1.0/qemu-kvm-x86.c b/qemu-kvm-1.0/qemu-kvm-x86.c --- a/qemu-kvm-1.0/qemu-kvm-x86.c 2011-12-04 19:38:06.000000000 +0900 +++ b/qemu-kvm-1.0/qemu-kvm-x86.c 2012-09-06 20:19:44.828163734 +0900 @@ -139,12 +139,28 @@ static int kvm_enable_tpr_access_reporti return kvm_vcpu_ioctl(env, KVM_TPR_ACCESS_REPORTING, &tac); } +static int kvm_set_slave_cpu(CPUState *env) +{ + int r, slave = env->cpu_index == 0 ? 2 : env->cpu_index == 1 ? 3 : -1; `slave' is the offlined CPU ID assigned, and `env->cpu_index' is the virtual CPU ID. You need to modify here and recompile qemu-kvm (or just offline cpu 2 and 3 for a 2vcpus guest ;) ). Thanks, Tomoki Sekiyama -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
