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From: | Anthony Liguori |
Subject: | [Qemu-devel] Re: Slowdowns comparing qemu-kvm.git to qemu.git: vcpu/thread scheduling differences |
Date: | Mon, 08 Feb 2010 08:57:05 -0600 |
User-agent: | Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.5) Gecko/20091209 Fedora/3.0-4.fc12 Lightning/1.0pre Thunderbird/3.0 |
On 02/08/2010 07:46 AM, Amit Shah wrote:
Hello, In my testing of virtio-console, I found qemu-kvm.git introduces a lot of overhead in thread scheduling compared to qemu.git. My test sends a 260M file from the host to a guest via a virtio-console port and then computes the sha1sum of the file on the host as well as on the guest, compares the checksum and declares the result based on the checksum match. The test passes in all the scenarios listed below, indicating there's no unsafe data transfer. Repo Time taken ----- ---------- qemu.git< 1 m (typically 30s) qemu-kvm.git> 16m qemu-iothread ~ 5m
That very likely suggests that there are missing qemu_notify_events() in qemu-kvm.git and you're getting blocked waiting for the next timer event to fire.
IOW, I assume that during the qemu-kvm.git run, the CPU isn't pegged at 100% whereas it is in qemu.git.
Regards, Anthony Liguori
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