When I increase fs.pipe-max-size like so (N is around 4-10Mbytes):

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

And then use F_SETPIPE_SZ to change named pipe sizes to N I sometimes get “operation not permitted” error.

The system has ~20 pipes and I set 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 because I use N that isn’t divisible by a memory 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” – make sense. I think I saw in logs values larger than I asked. Or is it something totally else?