Re: [PATCH net-next 1/3] perf, events: add non-linear data support for raw records

[Daniel Borkmann]

On 07/13/2016 06:40 PM, Peter Zijlstra wrote:
> On Wed, Jul 13, 2016 at 04:08:55PM +0200, Daniel Borkmann wrote:
> > On 07/13/2016 03:42 PM, Peter Zijlstra wrote:
> > > Ok so the nonlinear thing was it doing _two_ copies, one the regular
> > > __output_copy() on raw->data and second the optional fragment thingy
> > > using __output_custom().
> > >
> > > Would something like this work instead?
> > >
> > > It does the nonlinear thing and the custom copy function thing but
> > > allows more than 2 fragments and allows each fragment to have a custom
> > > copy.
> > >
> > > It doesn't look obviously more expensive; it has the one ->copy branch
> > > extra, but then it doesn't recompute the sizes.
> >
> > Yes, that would work as well on a quick glance with diff just a bit
> > bigger, but more generic this way. Do you want me to adapt this into
> > the first patch?
>
> Please.
>
> > One question below:
>
> > > -			u64 zero = 0;
>
> > > -			if (real_size - raw_size)
> > > -				__output_copy(handle, &zero, real_size - raw_size);
>
> > We still need the zero padding here from above with the computed
> > raw->size, right?
>
> Ah, yes, we need some __output*() in order to advance the handle offset.
> We don't _need_ to copy the 0s, but I doubt __output_skip() is much
> cheaper for these 1-3 bytes worth of data; we've already touched that
> line anyway.

Okay, thanks for your input! I'll respin then.