Timer problems on FreeBSD 11R on KVM

[Dmitry Marakasov]

* Dmitry Marakasov (amdmi3 at amdmi3.ru) wrote:

Virtualization problems keep raining on me. Or there seem to be exist
major FreeBSD problem when running under hypervisor.

Another VM under VMWare vSphere is now showing similar symptoms -
stable 33.3% intr load:

    3 users    Load  2.07  2.77  2.70                  Mar  6 15:53
   Mem usage:  95%Phy 58%Kmem
Mem: KB    REAL            VIRTUAL                      VN PAGER   SWAP PAGER
        Tot   Share      Tot    Share    Free           in   out     in   out
Act 1697056   15280  7672636    22792  739732  count
All 1700936   19060  7692936    42992          pages
Proc:                                                            Interrupts
  r   p   d   s   w   Csw  Trp  Sys  Int  Sof  Flt        ioflt   389 total
  2         166      1203  810  15k   20   92             cow         atkbd0 1
                                                          zfod     18 attimer0 0
 2.0%Sys  33.3%Intr  0.0%User  6.9%Nice 57.8%Idle         ozfod       fdc0 6
|    |    |    |    |    |    |    |    |    |           %ozfod       ata1 15
=+++++++++++++++++---                                     daefr       mpt0 17
                                           dtbuf          prcfr     2 em0 18
Namei     Name-cache   Dir-cache    350812 desvn          totfr   103 cpu0:timer
   Calls    hits   %    hits   %    344853 numvn          react    77 cpu2:timer
     326     326 100                316930 frevn          pdwak   189 cpu1:timer
                                                      219 pdpgs
Disks   da0   da1   da2   da3   cd0 pass0 pass1           intrn
KB/t   0.00  0.00  0.00  0.00  0.00  0.00  0.00  13835380 wire
tps       0     0     0     0     0     0     0    544104 act
MB/s   0.00  0.00  0.00  0.00  0.00  0.00  0.00   1219264 inact
%busy     0     0     0     0     0     0     0           cache
                                                   739732 free
                                                          buf

Switching to i8254 doesn't help either, load does not change, just
intrrupts move to attimer0.

This is box is not production so I can do whatever I like with it.

Here's dtrace output from /usr/share/dtrace/toolkit/hotkernel, but I
doubt it's helpful:

kernel`in_pcbref                                          790   4.2%
kernel`__rw_try_rlock                                    1054   5.6%
kernel`tcp_tw_2msl_scan                                  1419   7.5%
kernel`__rw_rlock                                        1433   7.6%
kernel`in_pcbrele_wlocked                                1846   9.7%
kernel`_rw_runlock_cookie                                2362  12.5%
kernel`acpi_cpu_c1                                       8615  45.5%

-- 
Dmitry Marakasov   .   55B5 0596 FF1E 8D84 5F56  9510 D35A 80DD F9D2 F77D
amdmi3 at amdmi3.ru  ..:  jabber: amdmi3 at jabber.ru      http://amdmi3.ru