3e2297140c
Change-Id: I0ffa5a8ea0ffb46113c6a000546a445784ce7b2f Signed-off-by: Darek Stojaczyk <dariusz.stojaczyk@intel.com> Reviewed-on: https://review.gerrithub.io/431094 Reviewed-by: Tomasz Zawadzki <tomasz.zawadzki@intel.com> Reviewed-by: Jim Harris <james.r.harris@intel.com> Reviewed-by: Ben Walker <benjamin.walker@intel.com> Tested-by: SPDK CI Jenkins <sys_sgci@intel.com> Chandler-Test-Pool: SPDK Automated Test System <sys_sgsw@intel.com>
30 lines
1.5 KiB
Markdown
30 lines
1.5 KiB
Markdown
# Virtio driver {#virtio}
|
|
|
|
# Introduction {#virtio_intro}
|
|
|
|
SPDK Virtio driver is a C library that allows communicating with Virtio devices.
|
|
It allows any SPDK application to become an initiator for (SPDK) vhost targets.
|
|
|
|
The driver supports two different usage models:
|
|
* PCI - This is the standard mode of operation when used in a guest virtual
|
|
machine, where QEMU has presented the virtio controller as a virtual PCI device.
|
|
* vhost-user - Can be used to connect to a vhost socket directly on the same host.
|
|
|
|
The driver, just like the SPDK @ref vhost, is using pollers instead of standard
|
|
interrupts to check for an I/O response. If used inside a VM, it bypasses interrupt
|
|
and context switching overhead of QEMU and guest kernel, significantly boosting
|
|
the overall I/O performance.
|
|
|
|
This Virtio library is currently used to implement two bdev modules:
|
|
@ref bdev_config_virtio_scsi and @ref bdev_config_virtio_blk.
|
|
These modules will export generic SPDK block devices usable by any SPDK application.
|
|
|
|
# 2MB hugepages {#virtio_2mb}
|
|
|
|
vhost-user specification puts a limitation on the number of "memory regions" used (8).
|
|
Each region corresponds to one file descriptor, and DPDK - as SPDK's memory allocator -
|
|
uses one file per hugepage by default. So *by default* this makes SPDK Virtio practical
|
|
with only 1GB hugepages. To run an SPDK app using Virtio initiator with 2MB hugepages
|
|
it is required to pass '-g' command-line option . This forces DPDK to create a single
|
|
non-physically-contiguous hugetlbfs file for all its memory.
|