Setting large fs.pipe-max-size

When I increase fs.pipe-max-size like so:

bash
echo "fs.pipe-max-size = N" >> /etc/sysctl.conf
sysctl -p

*(N is ~4-10Mbytes)* And use F_SETPIPE_SZ to change named pipe sizes to N, sometimes it fails with "operation not permitted" error. The system has ~20 pipes and I set the same pipe buffer size on all of them. The question is: - is it because I hit some kind of a total kernel pipe buffer memory capacity (btw the system has 30G RAM)? - Or is it because I use N that isn't divisible by a page size so F_SETPIPE_SZ might set the size above the fs.pipe-max-size limit and it will fail as "operation not permitted"? Makes sense, I think I saw in logs values larger than I asked. - Or is it something totally else?