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Subject: Re: [virtio-dev] [PATCH 0/2] introduce virtio-ism: internal shared memory device
Adding Stefan. On Mon, Oct 17, 2022 at 3:47 PM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote: > > Hello everyone, > > # Background > > Nowadays, there is a common scenario to accelerate communication between > different VMs and containers, including light weight virtual machine based > containers. One way to achieve this is to colocate them on the same host. > However, the performance of inter-VM communication through network stack is not > optimal and may also waste extra CPU cycles. This scenario has been discussed > many times, but still no generic solution available [1] [2] [3]. > > With pci-ivshmem + SMC(Shared Memory Communications: [4]) based PoC[5], > We found that by changing the communication channel between VMs from TCP to SMC > with shared memory, we can achieve superior performance for a common > socket-based application[5]: > - latency reduced by about 50% > - throughput increased by about 300% > - CPU consumption reduced by about 50% > > Since there is no particularly suitable shared memory management solution > matches the need for SMC(See ## Comparison with existing technology), and virtio > is the standard for communication in the virtualization world, we want to > implement a virtio-ism device based on virtio, which can support on-demand > memory sharing across VMs, containers or VM-container. To match the needs of SMC, > the virtio-ism device need to support: > > 1. Dynamic provision: shared memory regions are dynamically allocated and > provisioned. > 2. Multi-region management: the shared memory is divided into regions, > and a peer may allocate one or more regions from the same shared memory > device. > 3. Permission control: The permission of each region can be set seperately. Looks like virtio-ROCE https://lore.kernel.org/all/20220511095900.343-1-xieyongji@bytedance.com/T/ and virtio-vhost-user can satisfy the requirement? > > # Virtio ism device > > ISM devices provide the ability to share memory between different guests on a > host. A guest's memory got from ism device can be shared with multiple peers at > the same time. This shared relationship can be dynamically created and released. > > The shared memory obtained from the device is divided into multiple ism regions > for share. ISM device provides a mechanism to notify other ism region referrers > of content update events. > > # Usage (SMC as example) > > Maybe there is one of possible use cases: > > 1. SMC calls the interface ism_alloc_region() of the ism driver to return the > location of a memory region in the PCI space and a token. > 2. The ism driver mmap the memory region and return to SMC with the token > 3. SMC passes the token to the connected peer > 3. the peer calls the ism driver interface ism_attach_region(token) to > get the location of the PCI space of the shared memory > > > # About hot plugging of the ism device > > Hot plugging of devices is a heavier, possibly failed, time-consuming, and > less scalable operation. So, we don't plan to support it for now. > > # Comparison with existing technology > > ## ivshmem or ivshmem 2.0 of Qemu > > 1. ivshmem 1.0 is a large piece of memory that can be seen by all devices that > use this VM, so the security is not enough. > > 2. ivshmem 2.0 is a shared memory belonging to a VM that can be read-only by all > other VMs that use the ivshmem 2.0 shared memory device, which also does not > meet our needs in terms of security. > > ## vhost-pci and virtiovhostuser > > Does not support dynamic allocation and therefore not suitable for SMC. I think this is an implementation issue, we can support VHOST IOTLB message then the regions could be added/removed on demand. Thanks > > # Design > > This is a structure diagram based on ism sharing between two vms. > > |-------------------------------------------------------------------------------------------------------------| > | |------------------------------------------------| |------------------------------------------------| | > | | Guest | | Guest | | > | | | | | | > | | ---------------- | | ---------------- | | > | | | driver | [M1] [M2] [M3] | | | driver | [M2] [M3] | | > | | ---------------- | | | | | ---------------- | | | | > | | |cq| |map |map |map | | |cq| |map |map | | > | | | | | | | | | | | | | | | > | | | | ------------------- | | | | -------------------- | | > | |----|--|----------------| device memory |-----| |----|--|----------------| device memory |----| | > | | | | ------------------- | | | | -------------------- | | > | | | | | | | | > | | | | | | | | > | | Qemu | | | Qemu | | | > | |--------------------------------+---------------| |-------------------------------+----------------| | > | | | | > | | | | > | |------------------------------+------------------------| | > | | | > | | | > | -------------------------- | > | | M1 | | M2 | | M3 | | > | -------------------------- | > | | > | HOST | > --------------------------------------------------------------------------------------------------------------- > > # POC code > > Kernel: https://github.com/fengidri/linux-kernel-virtio-ism/commits/ism > Qemu: https://github.com/fengidri/qemu/commits/ism > > If there are any problems, please point them out. > > Hope to hear from you, thank you. > > [1] https://projectacrn.github.io/latest/tutorials/enable_ivshmem.html > [2] https://dl.acm.org/doi/10.1145/2847562 > [3] https://hal.archives-ouvertes.fr/hal-00368622/document > [4] https://lwn.net/Articles/711071/ > [5] https://lore.kernel.org/netdev/20220720170048.20806-1-tonylu@linux.alibaba.com/T/ > > > Xuan Zhuo (2): > Reserve device id for ISM device > virtio-ism: introduce new device virtio-ism > > content.tex | 3 + > virtio-ism.tex | 340 +++++++++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 343 insertions(+) > create mode 100644 virtio-ism.tex > > -- > 2.32.0.3.g01195cf9f > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org > For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org >
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