The Linux I/O law of fatherhood
Originally written by
- Whenever a read bio is submitted to a block device - the active thread
is accounted for it - regardless whether this is the originating process
- Whenever (virtual) memory pages are marked dirty - the active thread
is accounted for this as a write request.
- Why not during sending the bio to the block device?
- Because then we'll always think it was done by pdflush.
- Whenever pages in the page-cache are truncated - the active thread is
accounted for "cancelled write bytes" (i.e. "negative" I/O).