[OpenIndiana-discuss] zsf send/receive performance

[Jim Klimov]

Reading your description, I thought "can it be a single-CPU
performance issue?" Perhaps, decompressing your datasets
(or compressing upon write - though the /dev/null experiment
rules that out), or building the stream, or any other step
in your data path, might for some reason be a single-threaded
task. Running several in parallel splits them across many
cores, but one is slow.

Not being a ZFS developer, I am not ready to check and point
the place in code where that guess might be (dis-)proved,
but at least I'd start digging (and asking) with such an
assumption :)

At least, there are many things in parallel IT processing
that are made fast by sheer scale of concurrent independent
tasks, rather than (expensively) trying to parallelize the
code inside. And on average the cheap approach pays off ;)

//Jim