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We currently preallocate scatterlists which have 2048 entries for each command. For a small device with just 1 queue this results in: 8 MB = 32 bytes per sg * 2048 entries * 128 cmd When mq is turned on and we increase the virtqueue_size so we can handle commands from multiple queues in parallel, then this can sky rocket. This patch allows us to dynamically allocate the scatterlist like is done with drivers like NVMe and SCSI. For small IO (4-16K) IOPs testing, we didn't see any regressions, but for throughput testing we sometimes saw a 2-5% regression when the backend device was very fast (8 NVMe drives in a MD RAID0 config or a memory backed device). As a result this patch makes the dynamic allocation feature a modparam so userspace can decide how it wants to balance mem use and perf. Signed-off-by: Mike Christie <michael.christie@oracle.com> Message-Id: <20241203191705.19431-6-michael.christie@oracle.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
99 lines
2.5 KiB
Plaintext
99 lines
2.5 KiB
Plaintext
# SPDX-License-Identifier: GPL-2.0-only
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config VHOST_IOTLB
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tristate
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help
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Generic IOTLB implementation for vhost and vringh.
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This option is selected by any driver which needs to support
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an IOMMU in software.
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config VHOST_RING
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tristate
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select VHOST_IOTLB
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help
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This option is selected by any driver which needs to access
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the host side of a virtio ring.
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config VHOST_TASK
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bool
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default n
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config VHOST
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tristate
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select VHOST_IOTLB
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select VHOST_TASK
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help
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This option is selected by any driver which needs to access
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the core of vhost.
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menuconfig VHOST_MENU
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bool "VHOST drivers"
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default y
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if VHOST_MENU
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config VHOST_NET
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tristate "Host kernel accelerator for virtio net"
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depends on NET && EVENTFD && (TUN || !TUN) && (TAP || !TAP)
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select VHOST
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help
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This kernel module can be loaded in host kernel to accelerate
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guest networking with virtio_net. Not to be confused with virtio_net
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module itself which needs to be loaded in guest kernel.
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To compile this driver as a module, choose M here: the module will
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be called vhost_net.
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config VHOST_SCSI
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tristate "VHOST_SCSI TCM fabric driver"
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depends on TARGET_CORE && EVENTFD
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select VHOST
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select SG_POOL
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default n
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help
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Say M here to enable the vhost_scsi TCM fabric module
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for use with virtio-scsi guests
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config VHOST_VSOCK
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tristate "vhost virtio-vsock driver"
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depends on VSOCKETS && EVENTFD
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select VHOST
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select VIRTIO_VSOCKETS_COMMON
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default n
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help
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This kernel module can be loaded in the host kernel to provide AF_VSOCK
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sockets for communicating with guests. The guests must have the
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virtio_transport.ko driver loaded to use the virtio-vsock device.
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To compile this driver as a module, choose M here: the module will be called
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vhost_vsock.
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config VHOST_VDPA
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tristate "Vhost driver for vDPA-based backend"
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depends on EVENTFD
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select VHOST
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select IRQ_BYPASS_MANAGER
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depends on VDPA
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help
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This kernel module can be loaded in host kernel to accelerate
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guest virtio devices with the vDPA-based backends.
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To compile this driver as a module, choose M here: the module
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will be called vhost_vdpa.
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config VHOST_CROSS_ENDIAN_LEGACY
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bool "Cross-endian support for vhost"
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default n
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help
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This option allows vhost to support guests with a different byte
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ordering from host while using legacy virtio.
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Userspace programs can control the feature using the
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VHOST_SET_VRING_ENDIAN and VHOST_GET_VRING_ENDIAN ioctls.
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This is only useful on a few platforms (ppc64 and arm64). Since it
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adds some overhead, it is disabled by default.
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If unsure, say "N".
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endif
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