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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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| .. | ||
| bus.c | ||
| cpu.c | ||
| empty_slot.c | ||
| fw-path-provider.c | ||
| generic-loader.c | ||
| hotplug.c | ||
| irq.c | ||
| Kconfig | ||
| loader-fit.c | ||
| loader.c | ||
| machine-hmp-cmds.c | ||
| machine-qmp-cmds.c | ||
| machine.c | ||
| Makefile.objs | ||
| nmi.c | ||
| null-machine.c | ||
| numa.c | ||
| or-irq.c | ||
| platform-bus.c | ||
| ptimer.c | ||
| qdev-fw.c | ||
| qdev-properties-system.c | ||
| qdev-properties.c | ||
| qdev.c | ||
| register.c | ||
| reset.c | ||
| split-irq.c | ||
| stream.c | ||
| sysbus.c | ||
| trace-events | ||
| uboot_image.h | ||
| vm-change-state-handler.c | ||