r491: - Write out the keyring and cache headers every 60 seconds during operation, but only when there hasn't been any chardev I/O in 5 seconds (in an attempt to stay out of the critical path for I/O).  This allows "isr stat" to give a reasonable approximation against a running parcel, and limits the damage if vulpes crashes.
r491: - Write out the keyring and cache headers every 60 seconds during operation,
but only when there hasn't been any chardev I/O in 5 seconds (in an attempt
to stay out of the critical path for I/O).  This allows "isr stat" to give a
reasonable approximation against a running parcel, and limits the damage if
vulpes crashes.

cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr