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Date: Wed, 13 Jul 2016 16:08:55 +0200 From: Daniel Borkmann <daniel@...earbox.net> To: Peter Zijlstra <peterz@...radead.org> CC: davem@...emloft.net, alexei.starovoitov@...il.com, tgraf@...g.ch, netdev@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH net-next 1/3] perf, events: add non-linear data support for raw records Hi Peter, 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? One question below: > diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h > index 1fe22032f228..83e2a83e8db3 100644 > --- a/include/linux/perf_event.h > +++ b/include/linux/perf_event.h > @@ -69,9 +69,18 @@ struct perf_callchain_entry_ctx { > bool contexts_maxed; > }; > > +typedef unsigned long (*perf_copy_f)(void *dst, const void *src, unsigned long len); > + > +struct perf_raw_frag { > + struct perf_raw_frag *next; > + perf_copy_f copy; > + void *data; > + u32 size; > +} __packed; > + > struct perf_raw_record { > + struct perf_raw_frag frag; > u32 size; > - void *data; > }; > > /* > diff --git a/kernel/events/core.c b/kernel/events/core.c > index fe8d49a56322..f7ad7d65317d 100644 > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -5617,16 +5617,21 @@ void perf_output_sample(struct perf_output_handle *handle, > } > > if (sample_type & PERF_SAMPLE_RAW) { > - if (data->raw) { > - u32 raw_size = data->raw->size; > - u32 real_size = round_up(raw_size + sizeof(u32), > - sizeof(u64)) - sizeof(u32); > - u64 zero = 0; > - > - perf_output_put(handle, real_size); > - __output_copy(handle, data->raw->data, raw_size); > - if (real_size - raw_size) > - __output_copy(handle, &zero, real_size - raw_size); > + struct perf_raw_record *raw = data->raw; > + > + if (raw) { > + struct perf_raw_frag *frag = &raw->frag; > + > + perf_output_put(handle, raw->size); > + do { > + if (frag->copy) { > + __output_custom(handle, frag->copy, > + frag->data, frag->size); > + } else { > + __output_copy(handle, frag->data, frag->size); > + } > + frag = frag->next; > + } while (frag); We still need the zero padding here from above with the computed raw->size, right? > } else { > struct { > u32 size; > @@ -5751,14 +5756,22 @@ void perf_prepare_sample(struct perf_event_header *header, Thanks, Daniel
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