Re: [RFC HIFN 00/02]: RNG support

Re: [RFC HIFN 00/02]: RNG support

[Herbert Xu]

On Sun, Nov 18, 2007 at 04:30:40AM +0100, Patrick McHardy wrote:
>
> On a related issue, I think the rng interface is not very suitable
> for chips like HIFN that have a constant random bandwidth, it would
> make a lot more sense to return the time to wait to the core, instead
> of waiting 10us in all cases. 256 cycles at a speed of 266MHz comes
> down to 0.96us, so we're waiting about 10 times as long as necessary.
> Since its busy waiting anyway, I'd think that from a performance POV
> constant polling or returning the exact amount of time would be more
> reasonable.

I agree, a better interface would be to let the hardware do the
blocking where necessary.

Michael, what do you think about this?

Thanks,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: [RFC HIFN 00/02]: RNG support

[Herbert Xu]

On Sun, Nov 18, 2007 at 12:04:01PM +0800, Herbert Xu wrote:
> On Sun, Nov 18, 2007 at 04:30:40AM +0100, Patrick McHardy wrote:
> >
> > On a related issue, I think the rng interface is not very suitable
> > for chips like HIFN that have a constant random bandwidth, it would
> > make a lot more sense to return the time to wait to the core, instead
> > of waiting 10us in all cases. 256 cycles at a speed of 266MHz comes
> > down to 0.96us, so we're waiting about 10 times as long as necessary.
> > Since its busy waiting anyway, I'd think that from a performance POV
> > constant polling or returning the exact amount of time would be more
> > reasonable.
> 
> I agree, a better interface would be to let the hardware do the
> blocking where necessary.

I meant the hardware driver of course.

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: [RFC HIFN 00/02]: RNG support

[Michael Buesch]

On Sunday 18 November 2007 05:04:01 Herbert Xu wrote:
> On Sun, Nov 18, 2007 at 04:30:40AM +0100, Patrick McHardy wrote:
> >
> > On a related issue, I think the rng interface is not very suitable
> > for chips like HIFN that have a constant random bandwidth, it would
> > make a lot more sense to return the time to wait to the core, instead
> > of waiting 10us in all cases. 256 cycles at a speed of 266MHz comes
> > down to 0.96us, so we're waiting about 10 times as long as necessary.
> > Since its busy waiting anyway, I'd think that from a performance POV
> > constant polling or returning the exact amount of time would be more
> > reasonable.
> 
> I agree, a better interface would be to let the hardware do the
> blocking where necessary.
> 
> Michael, what do you think about this?

Patches are welcome. ;)

-- 
Greetings Michael.