Re: [Qemu-devel] [PATCH for-2.13] pc-bios/s390-ccw: Increase virtio timeout to 30 seconds

From: Cornelia Huck <cohuck@redhat.com>
To: Thomas Huth <thuth@redhat.com>
Cc: qemu-s390x@nongnu.org,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	qemu-devel@nongnu.org, ldoktor@redhat.com
Subject: Re: [Qemu-devel] [PATCH for-2.13] pc-bios/s390-ccw: Increase virtio timeout to 30 seconds
Date: Thu, 29 Mar 2018 15:15:05 +0200	[thread overview]
Message-ID: <20180329151505.36a28a74.cohuck@redhat.com> (raw)
In-Reply-To: <1522316251-16399-1-git-send-email-thuth@redhat.com>

On Thu, 29 Mar 2018 11:37:31 +0200
Thomas Huth <thuth@redhat.com> wrote:

> The current timeout is set to only three seconds - and considering that
> vring_wait_reply() or rather get_second() is not doing any rounding,
> the real timeout is likely rather 2 seconds in most cases. When the
> host is really badly loaded and we run the guest in TCG mode instead
> of KVM, it's possible that we hit this timeout by mistake. 

Let's tweak this sentence to

"When the host is really badly loaded, it's possible that we hit this
timeout by mistake; it's even more likely if we run the guest in TCG
mode instead of KVM."

?

> So let's
> increase the timeout to 30 seconds instead to ease this situation (30
> seconds is also the timeout that is used by the Linux SCSI subsystem
> for example, so this seems to be a sane value for block IO timeout).
> 
> Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1549079
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>  pc-bios/s390-ccw/virtio.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)