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SubjectRe: Still not sexy! (Re: sendfile+zerocopy: fairly sexy (nothing to do with ECN)


On Wed, 31 Jan 2001, Ingo Molnar wrote:

>
> On Tue, 30 Jan 2001, jamal wrote:
>
> > Kernel | tput | sender-CPU | receiver-CPU |
> > -------------------------------------------------
> > 2.4.0-pre3 | 99MB/s | 87% | 23% |
> > NSF | | | |
> > -------------------------------------------------
> > 2.4.0-pre3 | 68 | 8% | 8% |
> > +ZC SF | MB/s | | |
> > -------------------------------------------------
>
> isnt the CPU utilization difference amazing? :-)
>

With a caveat, sadly ;-> ttcp uses times() system call (or a diff of
times() one at the beggining and another at the end). So the cpu
measurements are not reflective.

> a couple of questions:
>
> - is this UDP or TCP based? (UDP i guess)
>
TCP

> - what wsize/rsize are you using? How do these requests look like on the
> network, ie. are they suffieciently MTU-sized?

yes. writes vary from 8K->64K but not much difference over the long period
of time.

>
> - what happens if you run multiple instances of the testcode, does it
> saturate bandwidth (or CPU)?

This is something of great interest. I havent tried it. I should.
I suspect this would be where the value of the ZC changes will become
evident.

cheers,
jamal

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