From: Jeff Furlong Date: Wed, 7 Mar 2018 00:53:20 +0000 (-0700) Subject: Reduce LOG_MSEC_SLACK X-Git-Tag: fio-3.6~55 X-Git-Url: https://git.kernel.dk/?p=fio.git;a=commitdiff_plain;h=674456bf7d0f775f774c8097c8bcb98b48cccc51;hp=674456bf7d0f775f774c8097c8bcb98b48cccc51 Reduce LOG_MSEC_SLACK Starting in fio 2.99, there is an odd problem when --ramp_time is used with --write_iops_log. The reported IOPs for the first ~200s or so are artificially inflated by fio, always monotonically increasing until about 200s, then resets to normal. With fio 2.99, disabling --ramp_time avoids the issue. And, with fio 2.21, using --ramp_time and --write_iops_log does not create the problem. Consider a job: fio --name=test --ioengine=libaio --direct=1 --rw=randread --iodepth=1 \\ --size=100% --bs=4k --filename=/dev/nvme1n1 --runtime=300s \\ --ramp_time=10s --write_iops_log=test --log_avg_msec=1000 See the attached plot for fio induced IOPs during the first ~200s. Using a longer runtime makes identifying the issue easier if the DUT is consistently performing. One simple method to resolve this inflation is by reducing the LOG_MSEC_SLACK from 10 milliseconds to 1 millisecond, given that we now operate some time structures to the nanosecond level (so 10ms of slack seems excessive). Below I also fixup some data type issues to match existing types (avoids typecasts or potential compiler warnings). Signed-off-by: Jens Axboe ---