Re: Stable kvm version ?

["David S. Ahern" <daahern@cisco.com>]

[-- Attachment #1: Type: text/plain, Size: 2340 bytes --]

There's a bug opened for the network lockups -- see
http://sourceforge.net/tracker/index.php?func=detail&aid=1802082&group_id=180599&atid=893831

Based on my testing I've found that the e1000 has the lowest overhead
(e.g., lowest irq and softirq times in the guest). I have not seen any
lockups with the network using the e1000 nic, and a couple of months ago
I was able to run a reasonably intensive network load continuously for
several days.

However, the duration tests I've run were with a modified BIOS. Months
ago when I was digging into the network lockups I was comparing
interrupt allocations to a DL320G3 running a RHEL3/4 load natively. I
noticed no interrupts were shared on bare hardware, while in my RHEL3/4
based kvm guests I was seeing interrupt sharing. So, I patched the bios
(see attached) to get a different usage.

I have not had time to do the due diligence to see if the stability was
due to kvm updates or my bios change. If you have the time I'd be
interested in knowing how the bios change works for you -- if you still
see lockups.

david


Freddie Cash wrote:
> On Fri, Jul 4, 2008 at 6:57 PM, David Mair <dmair@mair-family.org> wrote:
>> Slohm Gadaburi wrote:
>>> I found out I can't use Ubuntu's kvm package because it doesn't
>>> support vm snapshots.
>>>
>>> I am going to use a vanilla kvm and was wondering which version do you
>>> recommend me to use
>>> (my biggest concern is stability) ?
>> I have no stability problems with a mix of Windows and Linux guests using
>> kvm-70 on a x86_64 kernel 2.6.22.18. I've had one Linux guest up all of the
>> past week while testing something. YMMV.
> 
> I have no stability issues with kvm-69 on 64-bit Debian Lenny with
> kernel 2.6.24, using the kvm-amd module from the kernel package, when
> using the rtl8139 NIC.
> 
> I can lock up any of my VMs when using the e1000 NIC and doing massive
> data transfers (rsync, scp, wget), in Debian (Etch/Lenny), Windows XP
> (SP2/SP3), or FreeBSD (6.3/7.0) guests.  And also when using the
> virtio NIC or block drivers in Debian Lenny guests.  Haven't tracked
> down what causes the problem, or how to reliably cause it to happen
> (sometimes right away, sometimes it's fine for a week), which is why I
> haven't posted any bug reports on it as yet.
> 
> For now, all my VMs are using emulated NICs and block devices.

[-- Attachment #2: pci_irq.patch --]
[-- Type: text/x-patch, Size: 768 bytes --]

--- bios/rombios32.c.orig	2008-06-17 07:36:35.000000000 -0600
+++ bios/rombios32.c	2008-06-17 07:37:02.000000000 -0600
@@ -619,21 +619,21 @@
 
 typedef struct PCIDevice {
     int bus;
     int devfn;
 } PCIDevice;
 
 static uint32_t pci_bios_io_addr;
 static uint32_t pci_bios_mem_addr;
 static uint32_t pci_bios_bigmem_addr;
 /* host irqs corresponding to PCI irqs A-D */
-static uint8_t pci_irqs[4] = { 10, 10, 11, 11 };
+static uint8_t pci_irqs[4] = { 10, 11, 7, 3 };
 static PCIDevice i440_pcidev;
 
 static void pci_config_writel(PCIDevice *d, uint32_t addr, uint32_t val)
 {
     outl(0xcf8, 0x80000000 | (d->bus << 16) | (d->devfn << 8) | (addr & 0xfc));
     outl(0xcfc, val);
 }
 
 static void pci_config_writew(PCIDevice *d, uint32_t addr, uint32_t val)
 {