linux-kernel - Re: [PATCH V6] perf: Add PERF_SAMPLE_PHYS

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Date:   Wed, 23 Aug 2017 16:39:59 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     kan.liang@...el.com
Cc:     mingo@...hat.com, linux-kernel@...r.kernel.org, acme@...nel.org,
        jolsa@...hat.com, tglx@...utronix.de, eranian@...gle.com,
        ak@...ux.intel.com, mpe@...erman.id.au, maddy@...ux.vnet.ibm.com
Subject: Re: [PATCH V6] perf: Add PERF_SAMPLE_PHYS_ADDR

On Wed, Aug 23, 2017 at 04:33:08PM +0200, Peter Zijlstra wrote:
> > @@ -6145,6 +6183,9 @@ void perf_prepare_sample(struct perf_event_header *header,
> >  
> >  		header->size += size;
> >  	}
> > +
> > +	if (sample_type & PERF_SAMPLE_PHYS_ADDR)
> > +		data->phys_addr = perf_virt_to_phys(data->addr);
> 
> Only problem with this now is that it requires SAMPLE_ADDR to also be
> set in order to obtain data->addr.
> 
> Either fix all to set data->attr for (SAMPLE_ADDR || SAMPLE_PHYS_ADDR)
> or mandate SAMPLE_ADDR when SAMPLE_PHYS_ADDR.

I think the former suggestion is better, as it allows for smaller
samples.