kata-containers/tests/metrics/storage/fio-k8s/scripts/dax-compare-test

FIO in Kubernetes

This test runs fio jobs to measure how Kata Containers work using virtio-fs DAX. The test works using Kubernetes.
The test has to run in a single node cluster, it is needed as the test modifies Kata configuration file.

The virtio-fs options that this test will use are:

• cache mode Only auto, this is the most compatible mode for most of the Kata use cases. Today this is default in Kata.
• thread pool size Restrict the number of worker threads per request queue, zero means no thread pool.
• DAX

File contents can be mapped into a memory window on the host, allowing the guest to directly access data from the host page cache. This has several advantages: The guest page cache is bypassed, reducing the memory footprint.  No communication is necessary 
to access file contents, improving I/O performance. Shared file access is coherent between virtual machines on the same host even with mmap. 

This test by default iterates over different virtio-fs configurations.

test name	DAX	thread pool size	cache mode
pool_0_cache_auto_no_DAX	no	0	auto
pool_0_cache_auto_DAX	yes	0	auto

The fio options used are:

ioengine: How the IO requests are issued to the kernel.

• libaio: Supports async IO for both direct and buffered IO.
• mmap: File is memory mapped with mmap(2) and data copied to/from using memcpy(3).

rw type: Type of I/O pattern.

• randread: Random reads.
• randrw: Random mixed reads and writes.
• randwrite: Random writes.
• read: Sequential reads.
• write: Sequential writes.

Additional notes: Some jobs contain a multi prefix. This means that the same job runs more than once at the same time using its own file.

Static fio values:

Some fio values are not modified over all the jobs.

• runtime: Tell fio to terminate processing after the specified period of time(seconds).
• loops: Run the specified number of iterations of this job. Used to repeat the same workload a given number of times.
• iodepth: Number of I/O units to keep in flight against the file. Note that increasing iodepth beyond 1 will not affect synchronous ioengine.
• size: The total size of file I/O for each thread of this job.
• direct: If value is true, use non-buffered I/O. This is usually O_DIRECT.
• blocksize: The block size in bytes used for I/O units.