60 second CPU load spike

Jerry Van Baren vanbaren_gerald at si.com
Wed Feb 7 06:14:17 EST 2001

Did you check the file system synchronizing?  Traditionally, it happens
every 30 seconds, but it may be 60 seconds in your system.  Even if you
are running on a RAM disk, the system quite likely is doing a bdflush()

man update(8), bdflush(2)


At 10:33 AM 2/6/01 -0800, bkuschak at yahoo.com wrote:

>I was hoping someone might be able to provide a few hints or insights
>a problem I am trying to track down.  I've noticed that something in
>our system
>is spiking the CPU load exactly every 60 seconds.  When the system is
>loaded by packet processing, this spike causes the CPU to go to about
>100% (from
>80%) for approximately 2-3 seconds.  This causes packet drops at
>either the
>hardware or the netif_rx() backlog queue.  Here is some more information:
>- no other processes running except init, getty, sh, kswapd, kupdate,
>wdt (watchdog)
>- kernel instrumentation shows one 60-second timer (wdt), but it is not
>coincident with the spike
>- happens with ethernet IP-forwarding
>- profiling data inconclusive
>- using MontaVista's 2.4 kernel on PowerPC405
>I noticed 60 second periodic tasks such as route-related garbage
>etc, and changed these periods in /proc, without any effect.  I would
>like to
>find out what is causing these spikes and eliminate the problem.  Any
>would be appreciated.

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