[Samba] High CPU usage by rpc_server

[Jeremy Allison]

On Thu, Mar 29, 2018 at 01:18:16AM +0200, Karan Blas via samba wrote:
> We have two Samba AD-DC.
> 
> One is version 4.5.12 (debian) and 4.5.11 (ubuntu). On both, the rpc_server is using one core to the max 99-100% all the time.
> 
> I see the PID by samba-tool processes and I see something like 
> 
> dnsupdate              19526
> cldap_server           19520
> rpc_server             19515
> rpc_server             19515
> rpc_server             19515
> rpc_server             19515
> rpc_server             19515
> nbt_server             19517
> winbind_server         19528
> kdc_server             19521
> notify-daemon          19531
> ldap_server            19519
> kccsrv                 19525
> samba                      0
> dreplsrv               19522
> dnssrv                 19527
> 
> 
> The situation is same even at night with low load and if I shutdown one of them there is also no much difference. However if I copy the server in isolated environment it is silent ..1-5% CPU. We have around 1000 users. Can it be from the clients? At night there are less then 5 connections to the Samba:
> 
> netstat -tunepv | grep samba | wc -l

Can you attach to the process with strace and see what system calls it's making ?