Re: Very slow transfers to/from micro SD card on a RPi B+

[Taylor R Campbell <campbell+netbsd-tech-kern%mumble.net@localhost>]

   Date: Tue, 18 Aug 2015 14:30:55 +0200
   From: Stephan <stephanwib%googlemail.com@localhost>

   Does anybody have an idea on how to prove this? I don't know in what shape
   DTrace is (it's not enabled in amd64/arm yet, is it?), but the function
   boundary tracer might be of advantage here.

It's not, but it should be...  To enable it, build with `options
KDTRACE_HOOKS' in your kernel config and `MKDTRACE=yes' in your
mk.conf (or on the build.sh command line: `-V MKDTRACE=yes').

Then a basic thing to do for starters is

dtrace -n 'profile-97::: { @[stack()] = count(); }'

and ^C when you've done some file system operations to see the
profile.