linux-kernel - Re: [PATCH V8] perf: Add PERF_SAMPLE_PHYS

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Date:   Thu, 31 Aug 2017 13:43:27 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>,
        kan.liang@...el.com, mingo@...hat.com,
        linux-kernel@...r.kernel.org, jolsa@...hat.com, tglx@...utronix.de,
        eranian@...gle.com, ak@...ux.intel.com, mpe@...erman.id.au
Subject: Re: [PATCH V8] perf: Add PERF_SAMPLE_PHYS_ADDR

Em Tue, Aug 29, 2017 at 01:45:53PM +0200, Peter Zijlstra escreveu:
> On Tue, Aug 29, 2017 at 05:05:15PM +0530, Madhavan Srinivasan wrote:
> > 
> > 
> > On Tuesday 29 August 2017 06:22 AM, kan.liang@...el.com wrote:
> > > From: Kan Liang <kan.liang@...el.com>
> > > 
> > > For understanding how the workload maps to memory channels and hardware
> > > behavior, it's very important to collect address maps with physical
> > > addresses. For example, 3D XPoint access can only be found by filtering
> > > the physical address.
> > > 
> > > Add a new sample type for physical address.
> > > 
> > > perf already has a facility to collect data virtual address. This patch
> > > introduces a function to convert the virtual address to physical address.
> > > The function is quite generic and can be extended to any architecture as
> > > long as a virtual address is provided.
> > >   - For kernel direct mapping addresses, virt_to_phys is used to convert
> > >     the virtual addresses to physical address.
> > >   - For user virtual addresses, __get_user_pages_fast is used to walk the
> > >     pages tables for user physical address.
> > >   - This does not work for vmalloc addresses right now. These are not
> > >     resolved, but code to do that could be added.
> > > 
> > > The new sample type requires collecting the virtual address. The
> > > virtual address will not be output unless SAMPLE_ADDR is applied.
> > > 
> > > For security, the physical address can only be exposed to root or
> > > privileged user.
> > 
> > Tested-by: Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>

You mean you tested this together with Kan's v2 perf tools patches? If
that is so I'll add this tested-by to those patches, ok?
 
> Thanks maddy!