mirror of
https://github.com/xemu-project/xemu.git
synced 2024-11-28 22:10:33 +00:00
d0435bc513
Virtqueue notifications are not necessary during polling, so we disable them. This allows the guest driver to avoid MMIO vmexits. Unfortunately the virtio-blk and virtio-scsi handler functions re-enable notifications, defeating this optimization. Fix virtio-blk and virtio-scsi emulation so they leave notifications disabled. The key thing to remember for correctness is that polling always checks one last time after ending its loop, therefore it's safe to lose the race when re-enabling notifications at the end of polling. There is a measurable performance improvement of 5-10% with the null-co block driver. Real-life storage configurations will see a smaller improvement because the MMIO vmexit overhead contributes less to latency. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Message-Id: <20191209210957.65087-1-stefanha@redhat.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> |
||
|---|---|---|
| .. | ||
| dataplane | ||
| block.c | ||
| cdrom.c | ||
| ecc.c | ||
| fdc.c | ||
| hd-geometry.c | ||
| Kconfig | ||
| m25p80.c | ||
| Makefile.objs | ||
| nand.c | ||
| nvme.c | ||
| nvme.h | ||
| onenand.c | ||
| pflash_cfi01.c | ||
| pflash_cfi02.c | ||
| swim.c | ||
| tc58128.c | ||
| trace-events | ||
| vhost-user-blk.c | ||
| virtio-blk.c | ||
| xen_blkif.h | ||
| xen-block.c | ||