Re: [Xen-users] Xen boot time optimization

[Bertrand Marquis <Bertrand.Marquis@xxxxxxx>]

On 6 Mar 2020, at 05:50, Subhasree P V <subhasree.pv@xxxxxxxxxxxxxxxxxxx> wrote:

Thank you so much for your reply Bertrand.I have done it and was able to reduce about 520ms time..

Nice.

But still the delay before kernel load is the same.I think it is the time taken for the processing the interrupts.about 4s delay is there before kernel load.You can see it in the below log.

[2020-03-06 10:23:32.817] (XEN) Freed 264kB init memory.
[2020-03-06 10:23:36.719] [    0.000000] [c0] Booting Linux on physical CPU 0x0
[2020-03-06 10:23:36.719] [    0.000000] [c0] Initializing cgroup subsys cpu
[2020-03-06 10:23:36.724] [    0.000000] [c0] Initializing cgroup subsys cpuacct

I have tried by setting GICH_V2_LR_MAINTENANCE_IRQ only for non-hardware irqs and avoiding for hardware irqs.1s reduction in the delay has been there when i have done so.But dom0 kernel was not loading completely while doing so.It was hanging at some point.I thought the delay might be because of  too much inflight irqs.Could you please help me to solve it.

You are probably missing IRQs in Linux when you did that as the maintenance IRQ is needed by the vGIC.

Regarding the delay you see between “Freed” and first linux message it might be interesting to check if this time is actually spent in Xen or in Linux because the Freed is the last message printed by Xen here.

I cannot setup a system now to do some investigation on this but boot time with xen is something I will be definitely look at in the next months.

Regards

Bertrand

Thanks & Regards,

Subhasree

On Thu, Mar 5, 2020 at 10:47 PM Bertrand Marquis <Bertrand.Marquis@xxxxxxx> wrote:

Hi,

On 4 Mar 2020, at 10:40, Subhasree P V <subhasree.pv@xxxxxxxxxxxxxxxxxxx> wrote:

Hi,

I have been working with using XEN on ODROID-XU4 board.I would like to optimize the boot time of XEN to 3s. Currently it is taking about 5s to boot.I have disabled the prints.There is about 4s delay before kernel load.

Below is the log before disabling prints.

 
[2020-02-13 12:53:18.791] (XEN) Brought up 8 CPUs
[2020-02-13 12:53:18.791] (XEN) P2M: 40-bit IPA
[2020-02-13 12:53:18.791] (XEN) P2M: 3 levels with order-1 root, VTCR 0x80003558
[2020-02-13 12:53:18.797] (XEN) I/O virtualisation disabled
[2020-02-13 12:53:18.802] (XEN) *** LOADING DOMAIN 0 ***
[2020-02-13 12:53:18.802] (XEN) Loading kernel from boot module @ 0000000060000000
[2020-02-13 12:53:18.808] (XEN) Allocating 1:1 mappings totalling 1024MB for dom0:
[2020-02-13 12:53:19.578] (XEN) BANK[0] 0x00000070000000-0x000000b0000000 (1024MB)

This step takes 800ms

[2020-02-13 12:53:19.578] (XEN) Grant table range: 0x000000be800000-0x000000be861000
[2020-02-13 12:53:19.624] (XEN) Loading zImage from 0000000060000000 to 0000000077c00000-0000000077f08f60
[2020-02-13 12:53:19.649] (XEN) Allocating PPI 16 for event channel interrupt
[2020-02-13 12:53:19.649] (XEN) Loading dom0 DTB to 0x0000000078000000-0x000000007800c2f0
[2020-02-13 12:53:19.654] (XEN) Scrubbing Free RAM on 1 nodes using 8 CPUs

You probably want to disable scrubbing memory to speed up your boot (add bootscrub=no to your command line).

Regards

Bertrand

[2020-02-13 12:53:19.915] (XEN) ..done.
[2020-02-13 12:53:20.168] (XEN) Initial low memory virq threshold set at 0x4000 pages.
[2020-02-13 12:53:20.174] (XEN) Std. Loglevel: All
[2020-02-13 12:53:20.174] (XEN) Guest Loglevel: All
[2020-02-13 12:53:20.174] (XEN) Freed 264kB init memory.
[2020-02-13 12:53:24.274] [    0.000000] [c0] Booting Linux on physical CPU 0x0

I'm getting a delay after Freed 264kB init memory.I'm not able to figure out the reason for delay.Is there any way to reduce the delay?Please help me to solve this.

Thank you.

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