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We replaced Firecracker with QEMU

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Re: We replaced Firecracker with QEMU

#21

Post by andrewflnr »

londons_explore wrote: post #4

I really want VM's to integrate 'smarter' with the host. For example, if I'm running 5 VM's, there is a good chance that many of the pages are identical. Not only do I want those pages to be deduplicated, but I want them to be zero-copy (ie. not deduplicated after-the-fact by some daemon). To do that, the guest block cache needs to be integrated with the host block-cache, so that whenever some guest application tries…

Are you sure you're not thinking "copy on write" rather than "zero copy"? The latter implies you can predict in advance which pages will be the same forever...

Re: We replaced Firecracker with QEMU

#22

Post by anthk »

shrubble wrote: post #17
londons_explore wrote: post #4

I really want VM's to integrate 'smarter' with the host. For example, if I'm running 5 VM's, there is a good chance that many of the pages are identical. Not only do I want those pages to be deduplicated, but I want them to be zero-copy (ie. not deduplicated after-the-fact by some daemon). To do that, the guest block cache needs to be integrated with the host block-cache, so that whenever some guest application tries…

OpenVZ does this. If you have 5 VMs each loading the same library then memory is conserved, as I understand it.

kvm does the same with KSM.

Re: We replaced Firecracker with QEMU

#23

Post by arun-mani-j »

gwd wrote: post #3

Listen people, Firecracker is NOT A HYPERVISOR. A hypervisor runs right on the hardware. KVM is a hypervisor. Firecracker is a process that controls KVM. If you want to call firecracker (and QEMU, when used in conjunction with KVM) a VMM ("virtual machine monitor") I won't complain. But please please please, we need a word for what KVM and Xen are, and "hypervisor" is the best fit. Stop using that word for a user-lev…

I think you could help me answer the question that has been in my mind for a month :)

Is there any article that tells the difference and relationship between KVM, QEMU, libvirt, virt-manager, Xen, Proxmox etc. with their typical use cases?

Re: We replaced Firecracker with QEMU

#24

Post by lessaligned »

"the fork was very very bad for eating soup - this is a story about how we migrated to a spoon"

...firecracker does fine what it was designed to - short running fast start workloads.

(oh, and the article starts by slightly misusing a bunch of technical terms, firecracker's not technically a hypervisor per se)

Re: We replaced Firecracker with QEMU

#26

Post by zbrozek »

MuffinFlavored wrote: post #20
gwd wrote: post #3

Listen people, Firecracker is NOT A HYPERVISOR. A hypervisor runs right on the hardware. KVM is a hypervisor. Firecracker is a process that controls KVM. If you want to call firecracker (and QEMU, when used in conjunction with KVM) a VMM ("virtual machine monitor") I won't complain. But please please please, we need a word for what KVM and Xen are, and "hypervisor" is the best fit. Stop using that word for a user-lev…

> virtual machine monitor Is it good to think of libvirt as a virtual machine mointor, or is that more "virtual machine management"?

I'd love to get a clear explanation of what libvirt actually does. As far as I can tell it's a qemu argument assembler and launcher. For my own use-case, I just launch qemu from systemd unit files:

https://wiki.archlinux.org/title/QEMU#With_systemd_service

Re: We replaced Firecracker with QEMU

#27

Post by reactordev »

arun-mani-j wrote: post #23
gwd wrote: post #3

Listen people, Firecracker is NOT A HYPERVISOR. A hypervisor runs right on the hardware. KVM is a hypervisor. Firecracker is a process that controls KVM. If you want to call firecracker (and QEMU, when used in conjunction with KVM) a VMM ("virtual machine monitor") I won't complain. But please please please, we need a word for what KVM and Xen are, and "hypervisor" is the best fit. Stop using that word for a user-lev…

I think you could help me answer the question that has been in my mind for a month :) Is there any article that tells the difference and relationship between KVM, QEMU, libvirt, virt-manager, Xen, Proxmox etc. with their typical use cases?

KVM is kernel-based virtual machine, with libvirt being its API abstraction over all of it. QEMU is a virtual machine host that leverages kvm or software virtualization to spin up machines on the host. virt-manager does the same. Xen is another virtual machine host, like KVM. Proxmox is a virtual machine manager (like QEMU, virt-manager) but is web based. Libvirt will provide abstraction for kvm,qemu,xen

Use cases: proxmox web interface exposed on your local network on a KVM Linux box that uses QEMU to manage VM’s. Proxmox will allow you to do that from the web. QEMU is great for single or small fleet of machines but should be automated for any heavy lifting. Proxmox will do that.

Re: We replaced Firecracker with QEMU

#28

Post by rgbrenner »

"Firecracker's RAM footprint starts low, but once a workload inside allocates RAM, Firecracker will never return it to the host system."

Firecracker has a balloon device you can inflate (ie: acquire as much memory inside the VM as possible) and then deflate... returning the memory to the host. You can do this while the VM is running.

https://github.com/firecracker-microvm/firecracker/blob/main...

Re: We replaced Firecracker with QEMU

#29

Post by londons_explore »

andrewflnr wrote: post #21
londons_explore wrote: post #4

I really want VM's to integrate 'smarter' with the host. For example, if I'm running 5 VM's, there is a good chance that many of the pages are identical. Not only do I want those pages to be deduplicated, but I want them to be zero-copy (ie. not deduplicated after-the-fact by some daemon). To do that, the guest block cache needs to be integrated with the host block-cache, so that whenever some guest application tries…

Are you sure you're not thinking "copy on write" rather than "zero copy"? The latter implies you can predict in advance which pages will be the same forever...

The pages would be copy-on-write, but since this would mostly be for code pages, they would never be written, and therefore never copied.

By 'zero copy', I mean that when a guest tries to read a page, if another guest has that page in RAM, then no copy operation is done to get it into the memory space of the 2nd guest.

Re: We replaced Firecracker with QEMU

#30

Post by sheepscreek »

lessaligned wrote: post #24

"the fork was very very bad for eating soup - this is a story about how we migrated to a spoon" ...firecracker does fine what it was designed to - short running fast start workloads. (oh, and the article starts by slightly misusing a bunch of technical terms, firecracker's not technically a hypervisor per se)

..so is it more to support directly deploying functions to the cloud? Like, what AWS Lambda and CloudFront Functions might be built on?
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