Hi All, I am new to qemu development. Sorry If this is not the correct forum for this question, it would be great if you could direct me to correct forum.
I am seeing very low virtio network throughput on an older (2.6.18) linux guest vs another newer guest (3.10) both running on the same host. (same config 2 vcpus, no multi Q etc.) I see very high CPU usage on the 2.6.18 guest at very low network throughput and want to profile to find bottleneck. I tried to use "perf kvm" but the analysis shows overhead as max .25 % where as top in VM shows 100% cpu. (I used following as a guide https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html-single/Virtualization_Tuning_and_Optimization_Guide/index.html#sect-Virtualization_Tuning_Optimization_Guide-Monitoring_Tools-perf_kvm ) 0.25% :5235 [uhci_hcd] [g] 0xffffffff80182236 0.24% :5235 [uhci_hcd] [g] 0xffffffff8018226a 0.23% :5235 [virtio_ring] [g] vring_new_virtqueue 0.20% :5236 [uhci_hcd] [g] 0xffffffff80182236 0.18% :5236 [uhci_hcd] [g] 0xffffffff8018226a 0.18% :5235 [uhci_hcd] [g] 0xffffffff8016f385 0.14% :5236 [uhci_hcd] [g] 0xffffffff802fbe0f 0.14% :5235 [uhci_hcd] [g] 0xffffffff8001161a 0.14% :5235 [virtio_ring] [g] virtqueue_is_broken My basic question is - Is there a way I can profile the older version of linux guest so i can see the bottleneck (where the guest is spending CPU cycles) My aim is to see if i can patch the older version in the critical path with improvements made in newer version Thanks Kal
