round_blksz
blksz = round_blksz(bufsz >> blkcnt, bps);
sblksz = round_blksz(blksz, sndbuf_getalign(bs));
hblksz = round_blksz(sndbuf_xbytes(sblksz, bs, b),
hblksz = round_blksz(sndbuf_getmaxsize(b) >> 1,
nsblksz = round_blksz(