addd386d81
Also updated the CHANGELOG. Change-Id: I9040505f689aab51fc26ab47d5a10438e35f9fc4 Signed-off-by: Dariusz Stojaczyk <dariuszx.stojaczyk@intel.com> Reviewed-on: https://review.gerrithub.io/408830 Reviewed-by: Daniel Verkamp <daniel.verkamp@intel.com> Tested-by: SPDK Automated Test System <sys_sgsw@intel.com> Reviewed-by: John Kariuki <John.K.Kariuki@intel.com> Reviewed-by: Jim Harris <james.r.harris@intel.com>
34 lines
1.7 KiB
Markdown
34 lines
1.7 KiB
Markdown
# Virtio driver {#virtio}
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# Introduction {#virtio_intro}
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SPDK Virtio driver is a C library that allows communicating with Virtio devices.
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It allows any SPDK application to become an initiator for (SPDK) vhost targets.
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The driver supports two different usage models:
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* PCI - This is the standard mode of operation when used in a guest virtual
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machine, where QEMU has presented the virtio controller as a virtual PCI device.
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* vhost-user - Can be used to connect to a vhost socket directly on the same host.
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The driver, just like the SPDK @ref vhost, is using pollers instead of standard
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interrupts to check for an I/O response. If used inside a VM, it bypasses interrupt
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and context switching overhead of QEMU and guest kernel, significantly boosting
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the overall I/O performance.
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This Virtio library is currently used to implement two bdev modules:
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@ref bdev_config_virtio_scsi and @ref bdev_config_virtio_blk.
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These modules will export generic SPDK block devices usable by any SPDK application.
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# 2MB hugepages {#virtio_2mb}
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vhost-user specification puts a limitation on the number of "memory regions" used (8).
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Each region corresponds to one file descriptor, and DPDK - as SPDK's memory allocator -
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uses one file per hugepage by default. So *by default* this makes SPDK Virtio practical
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with only 1GB hugepages. To run an SPDK app using Virtio initiator with 2MB hugepages
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it is required to pass '-g' command-line option . This forces DPDK to create a single
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non-physically-contiguous hugetlbfs file for all its memory.
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This functionality requires latest DPDK changes that are officially landing in DPDK
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18.05, but have been also backported to spdk-18.02 branch of our internal DPDK fork
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which is currently used as a default git submodule for SPDK.
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