[Bug 247829] Constant load of 1 on a recent 12.1-STABLE with 3 ZFS pools (high rates of zfskern{mmp_thread_enter})

[bugzilla-noreply at freebsd.org]

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=247829

            Bug ID: 247829
           Summary: Constant load of 1 on a recent 12.1-STABLE with 3 ZFS
                    pools (high rates of zfskern{mmp_thread_enter})
           Product: Base System
           Version: 12.1-STABLE
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Many People
          Priority: ---
         Component: kern
          Assignee: bugs at FreeBSD.org
          Reporter: gbe at FreeBSD.org

On a recent virtualized 12.1-STABLE build I see a constant load of 1. While
investigating 'top -HS' it shows a relative high cpu usage for
'zfskern{mmp_thread_enter}', like in the example below.

  PID USERNAME    PRI NICE   SIZE    RES STATE    C   TIME    WCPU COMMAND
   11 root        155 ki31     0B    64K CPU2     2  17:28  97.39% idle{idle:
cpu2}
   11 root        155 ki31     0B    64K CPU3     3  17:29  96.78% idle{idle:
cpu3}
   11 root        155 ki31     0B    64K CPU1     1  17:29  96.40% idle{idle:
cpu1}
   11 root        155 ki31     0B    64K RUN      0  17:25  96.13% idle{idle:
cpu0}
    8 root         -8    -     0B  1040K mmp->m   2   0:44   4.32%
zfskern{mmp_thread_enter}
    8 root         -8    -     0B  1040K mmp->m   1   0:44   4.28%
zfskern{mmp_thread_enter}
    8 root         -8    -     0B  1040K mmp->m   3   0:44   4.25%
zfskern{mmp_thread_enter}

The problem at this point is that the relatively small CPU usage results in a
load=1.0, which let the host system schedule the assigned CPU cores of the VM
at the highest possible clockrate.

Trying OpenZFS seems to improve the situation, but I am not sure that this is
completely true, since only my zroot pool was detected and the two other pools
weren't.

-- 
You are receiving this mail because:
You are the assignee for the bug.