11.0 stuck on high network load

[Slawa Olhovchenkov]

On Wed, Sep 21, 2016 at 11:25:18PM +0200, Julien Charbon wrote:

> 
>  Hi Slawa,
> 
> On 9/21/16 9:51 PM, Slawa Olhovchenkov wrote:
> > On Wed, Sep 21, 2016 at 09:11:24AM +0200, Julien Charbon wrote:
> >>  You can also use Dtrace and lockstat (especially with the lockstat -s
> >> option):
> >>
> >> https://wiki.freebsd.org/DTrace/One-Liners#Kernel_Locks
> >> https://www.freebsd.org/cgi/man.cgi?query=lockstat&manpath=FreeBSD+11.0-RELEASE
> >>
> >>  But I am less familiar with Dtrace/lockstat tools.
> > 
> > I am still use old kernel and got lockdown again.
> > Try using lockstat (I am save more output), interesting may be next:
> > 
> > R/W writer spin on writer: 190019 events in 1.070 seconds (177571 events/sec)
> > 
> > -------------------------------------------------------------------------------
> > Count indv cuml rcnt     nsec Lock                   Caller                  
> > 140839  74%  74% 0.00    24659 tcpinp                 tcp_tw_2msl_scan+0xc6   
> > 
> >       nsec ------ Time Distribution ------ count     Stack                   
> >       4096 |                               913       tcp_twstart+0xa3        
> >       8192 |@@@@@@@@@@@@                   58191     tcp_do_segment+0x201f   
> >      16384 |@@@@@@                         29594     tcp_input+0xe1c         
> >      32768 |@@@@                           23447     ip_input+0x15f          
> >      65536 |@@@                            16197     
> >     131072 |@                              8674      
> >     262144 |                               3358      
> >     524288 |                               456       
> >    1048576 |                               9         
> > -------------------------------------------------------------------------------
> > Count indv cuml rcnt     nsec Lock                   Caller                  
> > 49180  26% 100% 0.00    15929 tcpinp                 tcp_tw_2msl_scan+0xc6   
> > 
> >       nsec ------ Time Distribution ------ count     Stack                   
> >       4096 |                               157       pfslowtimo+0x54         
> >       8192 |@@@@@@@@@@@@@@@                24796     softclock_call_cc+0x179 
> >      16384 |@@@@@@                         11223     softclock+0x44          
> >      32768 |@@@@                           7426      intr_event_execute_handlers+0x95
> >      65536 |@@                             3918      
> >     131072 |                               1363      
> >     262144 |                               278       
> >     524288 |                               19        
> > -------------------------------------------------------------------------------
> 
>  This is interesting, it seems that you have two call paths competing
> for INP locks here:
> 
>  - pfslowtimo()/tcp_tw_2msl_scan(reuse=0) and
> 
>  - tcp_input()/tcp_twstart()/tcp_tw_2msl_scan(reuse=1)

My current hypothesis:

nginx do write() (or may be close()?) to socket, kernel lock
first inp in V_twq_2msl, happen callout for pfslowtimo() on the same
CPU core and tcp_tw_2msl_scan infinity locked on same inp.

In this case you modification can't help, before next try we need some
like yeld().