Re: Route cache performance under stress

   From: Ben Greear [off-list ref]
   Date: Tue, 10 Jun 2003 18:15:36 -0700
   
   What determines whether or not we use the "TSC do_gettimeofday".  Does
   it automagically happen when you compile for P-III or something like
   that?
   
The 2.5.x kernel has x86 platform  drivers that decide this.

   And how big of a "bigger box" are you talking about...regular old
   SMP, or NUMA?

Many laptops cannot even use TSC reliably because of power management
etc. issues.

   > SO_RECVSTAMP, any socket on the machine can ask for this.
   
   Do we know when we are being asked for this value?

We have to take the timestamp at netif_receive_skb() for it to
be accurate.

We don't even know if this packet is for this host until a long
time later, let alone whether any local sockets want SO_RECVSTAMP
or whether any IP options want timestamp or whether tcpdump is
listening etc.