PPP performance

[Javi Lavandeira]

Hi,

I'm running a 4.6.2-RELEASE system on a PPPoE link, using user-ppp. Since
saturday, we're running a new service on this host, and we're getting
around 160 DNS requests/second, using tinydns, serving several zones. One
of them containing several hundred thousand records. Bandwidth usage is
low: around 25KBytes in and 80-100KBytes out average.

The problem is that now user-ppp seems to be eating up 25% of the CPU:

  PID USERNAME PRI NICE  SIZE    RES STATE    TIME   WCPU    CPU COMMAND
   76 root      30   0  3976K  2364K RUN    727:32 22.17% 22.17% ppp

This system has been running for more than a year, and there have been
transfer peaks of more than 20MBits/s, without impacting the ppp daemon in
this way.

Any ideas about why ppp is causing this load, and how to solve the
problem? I've been googling about this, and read something about
kernel-ppp being faster, but couldn't find anything about kernel-ppp in
the handbook.

Thanks in advance,