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() periodically.
man update(8), bdflush(2) gvb At 10:33 AM 2/6/01 -0800, bkuschak at yahoo.com wrote: >Hello, > >I was hoping someone might be able to provide a few hints or insights >regarding >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 >heavily >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, >kflushd, >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 >collection, >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 >comments >would be appreciated. > >Thanks, >Brian ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/