How much data can be fetched by submit_bio() at a time

Here is my LAN structure

I want to download a .zip file of 258.6MB from the samba server, meanwhile, start a profiling for the router's linu开发者_如何转开发x stack just before the download.

When finished, stopped the profiling and I found this in the porfiling report

samples   %       image name  app name  symbol name
...
16        0.0064  vmlinux     smbd      submit_bio
...

The sampling rate is 100000 and the event is CPU_CYCLES.

Because this is the first download of the file that is to say it is not in the page cache, submit_bio() should be pretty busy. Thus, I don't understand why there is just a poor portion of submit_bio(). Is that mean each time the submit_bio is called, we fetch about (258.6/16)MB data?

Thanks

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That's statistical sampling. It means of the x times the profiler sampled the system, 16 times it happened to find the CPU running in submit_bio(). It does not mean that submit_bio() is called 16 times.