Re: [Qemu-devel] [PATCH v2 0/2] pc: mmap kernel (ELF image) and initrd

[Montes, Julio]

Stefano, Brilliant job!

I can confirm that with these patches the memory footprint is smaller
and the boot time is the same for kata

Here the results using kata metrics

https://pasteboard.co/Ipl06Q0.png
https://pasteboard.co/Ipl3p4d.png

Thanks

-
Julio


On Tue, 2019-07-23 at 16:04 +0200, Stefano Garzarella wrote:
> In order to reduce the memory footprint when PVH kernel and initrd
> are used, we map them into memory instead of reading them.
> In this way we can share them between multiple instances of QEMU.
> 
> v2:
> - Patch 1: used g_mapped_file_new_from_fd() with 'writeble' set to
> 'true',
>            since we can modify the mapped buffer. [Paolo, Peter]
> 
> These are the results using a PVH kernel and initrd (cpio):
> - memory footprint (using smem) [MB]
>         QEMU              before                   now
>     # instances        USS      PSS            USS      PSS
>          1           102.0M   105.8M         102.3M   106.2M
>          2            94.6M   101.2M          72.3M    90.1M
>          4            94.1M    98.0M          72.0M    81.5M
>          8            94.0M    96.2M          71.8M    76.9M
>         16            93.9M    95.1M          71.6M    74.3M
> 
>     Initrd size: 3.0M
>     Kernel
>         image size: 28M
>         sections size [size -A -d vmlinux]:  18.9M
> 
> - boot time [ms]
>                           before                   now
>  qemu_init_end:           63.85                   55.91
>  linux_start_kernel:      82.11 (+18.26)          74.51 (+18.60)
>  linux_start_user:       169.94 (+87.83)         159.06 (+84.56)
> 
> QEMU command used:
> ./qemu-system-x86_64 -bios /path/to/seabios/out/bios.bin -no-hpet \
>     -machine
> q35,accel=kvm,kernel_irqchip,nvdimm,sata=off,smbus=off,vmport=off \
>     -cpu host -m 1G -smp 1 -vga none -display none -no-user-config
> -nodefaults \
>     -kernel /path/to/vmlinux -initrd /path/to/rootfs.cpio \
>     -append 'root=/dev/mem0 ro console=hvc0 pci=lastbus=0 nosmap'
> 
> Stefano Garzarella (2):
>   elf-ops.h: Map into memory the ELF to load
>   hw/i386/pc: Map into memory the initrd
> 
>  hw/i386/pc.c         | 15 ++++++++---
>  include/hw/elf_ops.h | 64 ++++++++++++++++++++++++----------------
> ----
>  2 files changed, 46 insertions(+), 33 deletions(-)
>