1e1fd9ac21
MD025 - Multiple top level headers in the same document Fixed all errors Update check_format.sh to fit new header style in jsonrpc.md Signed-off-by: Maciej Wawryk <maciejx.wawryk@intel.com> Change-Id: Ib5f832c549880771c99c15b89affe1e82acd3fa4 Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/9045 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> Community-CI: Broadcom CI <spdk-ci.pdl@broadcom.com> Community-CI: Mellanox Build Bot Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
31 lines
1.5 KiB
Markdown
31 lines
1.5 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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