Article ID: 119599, created on Jan 12, 2014, last review on May 11, 2014

  • Applies to:
  • Virtuozzo containers for Linux

Symptoms

The following messages may be found in the kernel log (dmesg output):

[root@hwnode ~]# dmesg | grep -i nohz
[ 9607.993815] NOHZ: local_softirq_pending 100
[16056.268035] NOHZ: local_softirq_pending 100

Cause

These messages indicate that the system puts CPUs to sleep state instead of processing some software interrupt.

The number in the end of line is expressed in hexadecimal form and it indicates the type of the interrupt, as a bit mask among all known types of interrupts as defined in the kernel sources, "include/linux/interrupt.h":

enum
{
    HI_SOFTIRQ=0,
    TIMER_SOFTIRQ,
    NET_TX_SOFTIRQ,
    NET_RX_SOFTIRQ,
    BLOCK_SOFTIRQ,
    BLOCK_IOPOLL_SOFTIRQ,
    TASKLET_SOFTIRQ,
    SCHED_SOFTIRQ,
    HRTIMER_SOFTIRQ,
    RCU_SOFTIRQ,    /* Preferable RCU should always be the last softirq */

    NR_SOFTIRQS
};

The number "100" is for "HRTIMER_SOFTIRQ", the software interrupt for high resolution (precision) timer, the interrupt can be skipped if a previous invocation is not finished yet.

Resolution

The situation is to be improved in the future release within the scope of the internal request PSBM-16366.

Search Words

softirq

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