From: Anthony Liguori <anthony@codemonkey.ws>
To: Amit Shah <amit.shah@redhat.com>
Cc: KVM List <kvm@vger.kernel.org>,
qemu-devel@nongnu.org, Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: Slowdowns comparing qemu-kvm.git to qemu.git: vcpu/thread scheduling differences
Date: Mon, 08 Feb 2010 08:57:05 -0600 [thread overview]
Message-ID: <4B702641.5060907@codemonkey.ws> (raw)
In-Reply-To: <20100208134645.GA19130@amit-x200.redhat.com>
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
WARNING: multiple messages have this Message-ID (diff)
From: Anthony Liguori <anthony@codemonkey.ws>
To: Amit Shah <amit.shah@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>,
qemu-devel@nongnu.org, KVM List <kvm@vger.kernel.org>
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 [thread overview]
Message-ID: <4B702641.5060907@codemonkey.ws> (raw)
In-Reply-To: <20100208134645.GA19130@amit-x200.redhat.com>
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
next prev parent reply other threads:[~2010-02-08 14:57 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-02-08 13:46 Slowdowns comparing qemu-kvm.git to qemu.git: vcpu/thread scheduling differences Amit Shah
2010-02-08 13:46 ` [Qemu-devel] " Amit Shah
2010-02-08 14:57 ` Anthony Liguori [this message]
2010-02-08 14:57 ` [Qemu-devel] " Anthony Liguori
2010-02-08 17:35 ` Amit Shah
2010-02-08 17:35 ` [Qemu-devel] " Amit Shah
2010-02-08 20:28 ` Anthony Liguori
2010-02-08 20:28 ` [Qemu-devel] " Anthony Liguori
2010-02-09 19:12 ` Jamie Lokier
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