zio_compress: introduce max size threshold

Now default compression is lz4, which can stop
compression process by itself on incompressible data.
If there are additional size checks -
we will only make our compressratio worse.

New usable compression thresholds are:
- less than BPE_PAYLOAD_SIZE (embedded_data feature);
- at least one saved sector.

Old 12.5% threshold is left to minimize affect
on existing user expectations of CPU utilization.

If data wasn't compressed - it will be saved as
ZIO_COMPRESS_OFF, so if we really need to recompress
data without ashift info and check anything -
we can just compress it with zero threshold.
So, we don't need a new feature flag here!

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: George Melikov <mail@gmelikov.ru>
Closes #9416

cmd/zstream/zstream_recompress.c

@@ -288,7 +288,8 @@ zstream_do_recompress(int argc, char *argv[])
 				abd_t *pabd =
 				    abd_get_from_buf_struct(&abd, buf, bufsz);
 				size_t csize = zio_compress_data(ctype, &dabd,
-				    &pabd, drrw->drr_logical_size, level);
+				    &pabd, drrw->drr_logical_size,
+				    drrw->drr_logical_size, level);
 				size_t rounded =
 				    P2ROUNDUP(csize, SPA_MINBLOCKSIZE);
 				if (rounded >= drrw->drr_logical_size) {