Hi! On 15:57 Sun 19 Apr , Jeffrey Cao wrote: > On 2009-04-17, Michael Blizek <michi1@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > > Hi! > > > > On 11:03 Fri 17 Apr , Devesh Sharma wrote: > >> Hello list, > >> > >> I have written a network device driver, and to validate it, I am > >> running a bandwidth measurement tool on it, > >> I am encountering a strange drop in bandwidth when data size reaches > >> to 4096, bandwidth figures drop form 24 Mbps (for 2k data size) > >> to .43 Mbps. what can be the problem, the MTU of my device is 2044. Is > >> it some how related to functioning of hard_start_xmit? > > > > What program/protocol do you use for testing + what kind of device is > > this? The CPU is not a bottleneck, is it? > > CPU causes problems only when you test with small packets, say 64 bytes > packets. Small packets will cause more frequent interrupt for the CPU. > If you can pass 24 Mbps with 2k data size, then you at least can pass > 24 Mbps with bigger packets. If you use UDP, the kernel has to fragment and concat big packets on IP layer. At least in theory, this can cause CPU usage to increase. -Michi -- programing a layer 3+4 network protocol for mesh networks see http://michaelblizek.twilightparadox.com -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
