Hi,
When stracing fio running on Linux (4.13) with libaio engine, I saw that
only one request is sent in the io_submit system call regardless of the
iodepth parameter value.
To see this:
strace -f fio --name=tmp --filename=/tmp/fio --filesize=8G \
--ioengine=libaio --bs=4k --iodepth=32 --rw=randwrite \
--runtime=10 2>&1 | grep io_submit
All of the lines look like this:
io_submit(140287955259392, 1, [{pwrite, fildes=3, str="...",
nbytes=4096, offset=1035223040}]) = 1
I would have expected to see the second parameter to be 32.
I see that the iodepth parameter has an impact in how many requests are
sent at the beginning (in this example, I see 32 requests sent), but
after that the requests are sent one by one as soon as one completes. I
understand this is done to keep the number of "requests in flight"
steady, but this is not what I expected when setting iodepth.
So is there a way to run fio so that we can send multiple requests per
io_submit call ?
Thanks,
Julien
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