Re: [Qemu-devel] [PATCH v4 0/3] pc: mmap kernel (ELF image) and initrd

[Paolo Bonzini]

On 24/07/19 16:31, 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.
> 
> v4:
>   - Patch 1: fix the rom_add_elf_program() comment [Paolo]
>   - Patch 2:
>     ~ fix the missing of g_mapped_file_unref() in the success case [Paolo]
>     ~ fix the rom_add_elf_program() comment [Paolo]
> 
> v3: https://patchew.org/QEMU/address@hidden/
> v2: https://patchew.org/QEMU/address@hidden/
> 
> 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 (3):
>   loader: Handle memory-mapped ELFs
>   elf-ops.h: Map into memory the ELF to load
>   hw/i386/pc: Map into memory the initrd
> 
>  hw/core/loader.c     | 38 +++++++++++++++++++-----
>  hw/i386/pc.c         | 17 ++++++++---
>  include/hw/elf_ops.h | 71 ++++++++++++++++++++++++++------------------
>  include/hw/i386/pc.h |  1 +
>  include/hw/loader.h  |  5 ++--
>  5 files changed, 89 insertions(+), 43 deletions(-)
> 

Queued, thanks.

Paolo