VFS/driver core overhead

[Valdis.Kletnieks at vt.edu]

On Mon, 06 Apr 2015 23:12:34 -0400, nick said:

(Replying mostly for the edification of those who can learn learn without
having to be spoon-fed)

> After reading through the code for the usb and vfs core infrastructure, I was wondering if
> after reading it if I am correct in my notion of there being very little overhead or none
> at all int these areas of the kernel. This is due to be noticing most drivers and file
> systems wrap around the core/vfs and therefore the overhead is very little and no need
> to worry about it like the overhead of the kernel's process structures based off task_struct

For bonus points, go learn the difference between latency and throughput, and
who cares about excessive overhead on each, and under what conditions, and
what solutions have already been tried to address the issue.

> .Honestly, I could benchmark this area of the kernel but it's hard to remove the file
> system/drivers interfering with my benchmarks due to me not knowing of any one way to do that.
> If someone either points me to a benchmark for me to test this or answers it that would be
> very helpful.

Step -1: Go back and re-read the recent postings about diagnosing slow kernel
builds, because you apparently didn't actually learn anything from them.

Step 0: Learn enough about proper benchmarking and the thing you're
benchmarking to be able to ask a meaningful, answerable question.

Step 1: Go find the proper tool for testing your question.

Step 2: Do the measurement needed to answer your question.
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