On Sat, 27 Jan 2001, Andrew Morton wrote:
> (Please keep netdev copied, else Jamal will grump at you, and
> you don't want that).
>
Thanks, Andrew ;-> Isnt netdev where networking stuff should be
discussed? I think i give up and will join lk, RSN ;->
> The kernels which were tested were 2.4.1-pre10 with and without the
> zerocopy patch. We only look at client load (the TCP sender).
>
> The link throughput was 11.5 mbytes/sec at all times (saturated 100baseT)
>
> 2.4.1-pre10-vanilla, using sendfile(): 29.6% CPU
> 2.4.1-pre10-vanilla, using read()/write(): 34.5% CPU
>
> 2.4.1-pre10+zercopy, using sendfile(): 18.2% CPU
> 2.4.1-pre10+zercopy, using read()/write(): 38.1% CPU
>
> 2.4.1-pre10+zercopy, using sendfile(): 22.9% CPU * hardware tx checksums
>disabled
> 2.4.1-pre10+zercopy, using read()/write(): 39.2% CPU * hardware tx checksums
>disabled
>
>
> What can we conclude?
>
> - sendfile is 10% cheaper than read()-then-write() on 2.4.1-pre10.
>
> - sendfile() with the zerocopy patch is 40% cheaper than
> sendfile() without the zerocopy patch.
>
It is also useful to have both client and server stats.
BTW, since the laptop (with the 3C card) is the client, the SG
shouldnt kick in at all.
> - hardware Tx checksums don't make much difference. hmm...
>
> Bear in mind that the 3c59x driver uses a one-interrupt-per-packet
> algorithm. Mitigation reduces this to 0.3 ints/packet.
> So we're absorbing 4,500 interrupts/sec while processing
> 12,000 packets/sec. gigE NICs do much better mitigation than
> this and the relative benefits of zerocopy will be much higher
> for these. Hopefully Jamal can do some testing.
>
I dont have my babies right now, but as soon as i can get access to
them
> BTW: I could not reproduce Jamal's oops when sending large
> files (2 gigs with sendfile()).
Alexey was concerned about this. Good. But maybe it will still
happen with my setupo. We'll see.
>
> The test tool is, of course, documented [ :-)/2 ]. It's at
>
> http://www.uow.edu.au/~andrewm/linux/#zc
>
I'll give this a shot later. Can you try with the sendfiled-ttcp?
http://www.cyberus.ca/~hadi/ttcp-sf.tar.gz
Anyways, you are NIC-challenged ;-> Get GigE. 100Mbps doesnt give
much information.
cheers,
jamal
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