On 24/07/2017 7:53, Kinsella, Ray wrote:
Hi Ray,
Thank you for the details,
So as it turns out at 512 devices, it is nothing to do SeaBIOS, it was the
Kernel again.
It is taking quite a while to startup, a little over two hours (7489 seconds).
The main culprits appear to be enumerating/initializing the PCI Express ports
and enabling interrupts.
The PCI Express Root Ports are taking a long time to enumerate/ initializing.
42 minutes in total=2579/60=64 ports in total, 40 seconds each.
Even if I am not aware of how much time would take to init a bare-metal
PCIe Root Port, it seems too much.
[ 50.612822] pci_bus 0000:80: root bus resource [bus 80-c1]
[ 172.345361] pci 0000:80:00.0: PCI bridge to [bus 81]
...
[ 2724.734240] pci 0000:80:08.0: PCI bridge to [bus c1]
[ 2751.154702] ACPI: Enabled 2 GPEs in block 00 to 3F
I assume the 1 hour (3827 seconds) below is being spent enabling interrupts.
Assuming you are referring to legacy interrupts, maybe is possible
to disable them and use only MSI/MSI-X for PCIe Root Ports
(based on user input, we can't disable INTx for all the ports)
[ 2899.394288] ACPI: PCI Interrupt Link [GSIG] enabled at IRQ 22
[ 2899.531324] ACPI: PCI Interrupt Link [GSIH] enabled at IRQ 23
[ 2899.534778] ACPI: PCI Interrupt Link [GSIE] enabled at IRQ 20
[ 6726.914388] Serial: 8250/16550 driver, 4 ports, IRQ sharing disabled
[ 6726.937932] 00:04: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a
16550A
[ 6726.964699] Linux agpgart interface v0.103
There finally there is another 20 minutes to find in the boot.
[ 7489.202589] virtio_net virtio515 enp193s0f0: renamed from eth513
Poky (Yocto Project Reference Distro) 2.3 qemux86-64 ttyS0
qemux86-64 login: root
I will remove the virtio-net-pci devices and hotplug them instead.
In theory it should improve boot time, at expense of incurring some of these
costs at runtime.
I would appreciate if you can share the results.
Thanks,
Marcel
Ray K
-----Original Message-----
From: Kevin O'Connor [mailto:ke...@koconnor.net]
Sent: Sunday, July 23, 2017 1:05 PM
To: Marcel Apfelbaum <mar...@redhat.com>; Kinsella, Ray <ray.kinse...@intel.com>
Cc: qemu-devel@nongnu.org; seab...@seabios.org; Gerd Hoffmann <kra...@redhat.com>;
Michael Tsirkin <m...@redhat.com>
Subject: Re: >256 Virtio-net-pci hotplug Devices
On Sun, Jul 23, 2017 at 07:28:01PM +0300, Marcel Apfelbaum wrote:
On 22/07/2017 2:57, Kinsella, Ray wrote:
When scaling up to 512 Virtio-net devices SeaBIOS appears to really
slow down when configuring PCI Config space - haven't manage to get
this to work yet.
If there is a slowdown in SeaBIOS, it would help to produce a log with timing
information - see:
https://www.seabios.org/Debugging#Timing_debug_messages
It may also help to increase the debug level in SeaBIOS to get more fine
grained timing reports.
-Kevin
