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Date:      Tue, 21 Aug 2018 19:20:42 +0000
From:      bugzilla-noreply@freebsd.org
To:        bugs@FreeBSD.org
Subject:   [Bug 230808] rand_harvestq high CPU utilization
Message-ID:  <bug-230808-227@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D230808

            Bug ID: 230808
           Summary: rand_harvestq high CPU utilization
           Product: Base System
           Version: CURRENT
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Only Me
          Priority: ---
         Component: kern
          Assignee: bugs@FreeBSD.org
          Reporter: danilo@FreeBSD.org

I'm seeing a high CPU utilization by the thread rand_harvestq.

It's easily reproducible in my system, just reading from /dev/urandom for 2
seconds is enough to trigger this issue. The rand_harvestq start eating CPU=
 for
minutes and the system (at least the graphical interface) start freezing for
few seconds.

After some minutes the thread stop the high CPU consumption and the system =
stop
freezing.

 PID USERNAME    PRI NICE   SIZE    RES STATE    C   TIME    WCPU COMMAND
   19 root       -16    -      0    16K CPU3     3   6:31 100.00% rand_harv=
estq
   11 root       155 ki31      0    64K CPU2     2 327:17  98.30% idle{idle:
cpu2}
   11 root       155 ki31      0    64K RUN      3 323:58  69.61% idle{idle:
cpu3}
   11 root       155 ki31      0    64K CPU0     0 325:32  69.01% idle{idle:
cpu0}
   11 root       155 ki31      0    64K RUN      1 327:07  58.61% idle{idle:
cpu1}

 PID USERNAME    PRI NICE   SIZE    RES STATE    C   TIME    WCPU COMMAND
   19 root       -16    -      0    16K CPU1     1  27:50  99.98% rand_harv=
estq
   11 root       155 ki31      0    64K CPU2     2 359:58  98.65% idle{idle:
cpu2}
   11 root       155 ki31      0    64K RUN      3 351:16  98.41% idle{idle:
cpu3}
   11 root       155 ki31      0    64K CPU0     0 357:59  94.45% idle{idle:
cpu0}
   11 root       155 ki31      0    64K RUN      1 345:23   4.51% idle{idle:
cpu1}


  PID USERNAME    PRI NICE   SIZE    RES STATE    C   TIME    WCPU COMMAND
   19 root       -16    -      0    16K CPU3     3  28:16 100.00% rand_harv=
estq
   11 root       155 ki31      0    64K CPU0     0 358:24  97.82% idle{idle:
cpu0}
   11 root       155 ki31      0    64K RUN      2 360:23  97.78% idle{idle:
cpu2}
   11 root       155 ki31      0    64K RUN      3 351:36  70.94% idle{idle:
cpu3}
   11 root       155 ki31      0    64K CPU1     1 345:31  25.92% idle{idle:
cpu1}


More information about my setup

$ uname -a
FreeBSD capeta 12.0-ALPHA2 FreeBSD 12.0-ALPHA2 #14 r337973M: Fri Aug 17
13:03:01 -03 2018=20=20=20=20
danilo@capeta:/usr/obj/usr/src/amd64.amd64/sys/GENERIC-NODEBUG  amd64

$ sysctl kern.random
kern.random.fortuna.minpoolsize: 64
kern.random.harvest.mask_symbolic:
PURE_RDRAND,[UMA],[FS_ATIME],SWI,INTERRUPT,NET_NG,NET_ETHER,NET_TUN,MOUSE,K=
EYBOARD,ATTACH,CACHED
kern.random.harvest.mask_bin: 00000010000000111111111
kern.random.harvest.mask: 66047
kern.random.random_sources: 'Intel Secure Key RNG'

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