From: Surbhi Palande <csurbhi@gmail.com>
To: fio@vger.kernel.org
Subject: fio - write benchmark help requested
Date: Tue, 12 Dec 2023 18:01:44 -0800 [thread overview]
Message-ID: <CAMBkX3d4d2ex+pTnS9iGL+uqbdaGKL3MYnt_HRhORAoosf07PQ@mail.gmail.com> (raw)
Hello All,
I am emailing here to understand how fio can be used to benchmark
writes in synchronous and asynchronous mode. I have wasted some time
in running some benchmarks the wrong way. I am sending this email in
the hopes that someone can throw light my way.
As I understand it, unless "direct = 1", synchronous write will occur
in the page cache and thus will not show the storage device's write
bandwidth.
--------------------------------
*Synchronous writes that reflect the device bandwidth/iops can be
performed in two ways:
ioengine = sync,
direct = 1
buffered =0
OR
ioengine = libaio/io_uring
direct = 1
iodepth = 1
-------------------------------------
Asynchronous writes that reflect the device bandwidth/iops can be
performed in the following ways:
ioengine = libaio
direct = 1
iodepth = "x"
io_batch = "y" [where y < x ]
or
ioengine = io_uring
direct = 1
iodepth = "x"
iodepth_batch = "y" [where y < x ]
If I want to maximize the requests that get sent to the device, I can
specify a huge iodepth number. The Linux kernel will then keep sending
the device the maximum I/O requests that the device can accept (true
queue depth of the storage device).
However, I am not sure how to control the actual queue depth when that
is not the case.
If I want the CMR drive (my storage device) to consistently get 4
requests at a time:
setting iodepth = 4 will not control it. This will only control that
the device will have at a maximum 4 requests at a time, but it cannot
control the minimum.
Is this understanding correct?
Best Regards,
Surbhi
reply other threads:[~2023-12-13 2:01 UTC|newest]
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