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1bf8a989a5
Before the patch, seg_max parameter was immutable and hardcoded to 126 (128 - 2) without respect to queue size. This has two negative effects: 1. when queue size is < 128, we have Virtio 1.1 specfication violation: (2.6.5.3.1 Driver Requirements) seq_max must be <= queue_size. This violation affects the old Linux guests (ver < 4.14). These guests crash on these queue_size setups. 2. when queue_size > 128, as was pointed out by Denis Lunev <den@virtuozzo.com>, seg_max restrics guest's block request length which affects guests' performance making them issues more block request than needed. https://lists.gnu.org/archive/html/qemu-devel/2017-12/msg03721.html To mitigate this two effects, the patch adds the property adjusting seg_max to queue size automaticaly. Since seg_max is a guest visible parameter, the property is machine type managable and allows to choose between old (seg_max = 126 always) and new (seg_max = queue_size - 2) behaviors. Not to change the behavior of the older VMs, prevent setting the default seg_max_adjust value for older machine types. Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Denis Plotnikov <dplotnikov@virtuozzo.com> Message-Id: <20191220140905.1718-2-dplotnikov@virtuozzo.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> |
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| .. | ||
| emulation.c | ||
| esp-pci.c | ||
| esp.c | ||
| Kconfig | ||
| lsi53c895a.c | ||
| Makefile.objs | ||
| megasas.c | ||
| mfi.h | ||
| mpi.h | ||
| mptconfig.c | ||
| mptendian.c | ||
| mptsas.c | ||
| mptsas.h | ||
| scsi-bus.c | ||
| scsi-disk.c | ||
| scsi-generic.c | ||
| spapr_vscsi.c | ||
| srp.h | ||
| trace-events | ||
| vhost-scsi-common.c | ||
| vhost-scsi.c | ||
| vhost-user-scsi.c | ||
| viosrp.h | ||
| virtio-scsi-dataplane.c | ||
| virtio-scsi.c | ||
| vmw_pvscsi.c | ||
| vmw_pvscsi.h | ||