[PATCH 0/3] Performance enhancements

Keith Busch
2017-12-21T20:46:33Z

A few IO micro-optimizations for IO polling and NVMe. I'm really working
to close the performance gap with userspace drivers, and this gets me
halfway there on latency. The fastest hardware I could get measured
roundtrip read latency at 5usec with this series that was previously
measuring 5.7usec.

Note with NVMe, you really need to crank up the interrupt coalescing to
see the completion polling benefit.

Test pre-setup:

echo performance | tee /sys/devices/system/cpu/cpufreq/policy*/scaling_governor
echo 0 > /sys/block/nvme0n1/queue/iostats
echo -1 > /sys/block/nvme0n1/queue/io_poll_delay
nvme set-feature /dev/nvme0 -f 8 -v 0x4ff

fio profile:

[global]
ioengine=pvsync2
rw=randread
norandommap
direct=1
bs=4k
hipri

[hi-pri]
filename=/dev/nvme0n1
cpus_allowed=2

Keith Busch (3):
nvme/pci: Start request after doorbell ring
nvme/pci: Remove cq_vector check in IO path
block: Polling completion performance optimization

drivers/nvme/host/pci.c | 14 +++-----------
fs/block_dev.c | 5 ++++-
2 files changed, 7 insertions(+), 12 deletions(-)

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2.13.6