[ceph.git] / ceph / src / spdk / test / lib / nvme / overhead / README

This application measures the software overhead of I/O submission
and completion for both the SPDK NVMe driver and an AIO file handle.
It runs a random read, queue depth = 1 workload to a single device,
and captures TSC as follows:

* Submission: capture TSC before and after the I/O submission
  call (SPDK or AIO).
* Completion: capture TSC before and after the I/O completion
  check.  Only record the TSC delta if the I/O completion check
  resulted in a completed I/O.  Also use heuristics in the AIO
  case to account for time spent in interrupt handling outside
  of the actual I/O completion check.

Usage:

To test software overhead for a 4KB I/O over a 10 second period:

SPDK:  overhead -s 4096 -t 10
AIO:   overhead -s 4096 -t 10 /dev/nvme0n1

Note that for the SPDK case, it will only use the first namespace
on the first controller found by SPDK.  If a different namespace is
desired, attach controllers individually to the kernel NVMe driver
to ensure they will not be enumerated by SPDK.
Commit	Line	Data
7c673cae FG	1	This application measures the software overhead of I/O submission
	2	and completion for both the SPDK NVMe driver and an AIO file handle.
	3	It runs a random read, queue depth = 1 workload to a single device,
	4	and captures TSC as follows:
	5
	6	* Submission: capture TSC before and after the I/O submission
	7	call (SPDK or AIO).
	8	* Completion: capture TSC before and after the I/O completion
	9	check. Only record the TSC delta if the I/O completion check
	10	resulted in a completed I/O. Also use heuristics in the AIO
	11	case to account for time spent in interrupt handling outside
	12	of the actual I/O completion check.
	13
	14	Usage:
	15
	16	To test software overhead for a 4KB I/O over a 10 second period:
	17
	18	SPDK: overhead -s 4096 -t 10
	19	AIO: overhead -s 4096 -t 10 /dev/nvme0n1
	20
	21	Note that for the SPDK case, it will only use the first namespace
	22	on the first controller found by SPDK. If a different namespace is
	23	desired, attach controllers individually to the kernel NVMe driver
	24	to ensure they will not be enumerated by SPDK.