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It seems like the addition of QUEUE_FLAG_VIRT caueses major performance regressions for Fedora users: https://bugzilla.redhat.com/show_bug.cgi?id=509383 https://bugzilla.redhat.com/show_bug.cgi?id=505695 while I can't reproduce those extreme regressions myself I think the flag is wrong. Rationale: QUEUE_FLAG_VIRT expands to QUEUE_FLAG_NONROT which casus the queue unplugged immediately. This is not a good behaviour for at least qemu and kvm where we do have significant overhead for every I/O operations. Even with all the latested speeups (native AIO, MSI support, zero copy) we can only get native speed for up to 128kb I/O requests we already are down to 66% of native performance for 4kb requests even on my laptop running the Intel X25-M SSD for which the QUEUE_FLAG_NONROT was designed. If we ever get virtio-blk overhead low enough that this flag makes sense it should only be set based on a feature flag set by the host. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> |
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aoe | ||
paride | ||
amiflop.c | ||
ataflop.c | ||
brd.c | ||
cciss_cmd.h | ||
cciss_scsi.c | ||
cciss_scsi.h | ||
cciss.c | ||
cciss.h | ||
cpqarray.c | ||
cpqarray.h | ||
cryptoloop.c | ||
DAC960.c | ||
DAC960.h | ||
floppy.c | ||
hd.c | ||
ida_cmd.h | ||
ida_ioctl.h | ||
Kconfig | ||
loop.c | ||
Makefile | ||
mg_disk.c | ||
nbd.c | ||
osdblk.c | ||
pktcdvd.c | ||
ps3disk.c | ||
ps3vram.c | ||
smart1,2.h | ||
sunvdc.c | ||
swim3.c | ||
swim_asm.S | ||
swim.c | ||
sx8.c | ||
ub.c | ||
umem.c | ||
umem.h | ||
viodasd.c | ||
virtio_blk.c | ||
xd.c | ||
xd.h | ||
xen-blkfront.c | ||
xsysace.c | ||
z2ram.c |