I am trying to understand the Linux block layer so I am writing a blog about it: http://www.linuxintro.org/wiki/blktrAce. When calling blktrace like this:
blktrace -d /dev/sdg -o - | blkparse -i -
I see e.g. the output
8,96 4 695 430.080106382 2356 I N 0 (00 ..) [kworker/4:2] 8,96 3 29 430.082179440 53 D N 0 (00 ..) [ksoftirqd/3]
I do not understand what this means. According to the man page of blkparse, there is an RWBS field (containing R for read, W for write, B for barrier, D for discard or S for sync). With some experimenting I found out it is the 7th column. However it contains N. What does that mean? Where can I find the info what it means?