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

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Date:   Fri, 1 Sep 2017 13:02:14 +0000
From:   "Liang, Kan" <kan.liang@...el.com>
To:     Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
CC:     "mingo@...hat.com" <mingo@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "jolsa@...hat.com" <jolsa@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "eranian@...gle.com" <eranian@...gle.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "mpe@...erman.id.au" <mpe@...erman.id.au>
Subject: RE: [PATCH V8] perf: Add PERF_SAMPLE_PHYS_ADDR

> On Thursday 31 August 2017 10:13 PM, Arnaldo Carvalho de Melo wrote:
> 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?
> Arnaldo,
> 
> No. Kernel side patch showed the link for the v1 of the perf tool side
> patchset (5 patch series) and I used that to test.
>

Thanks Maddy for the test.
Yes, the kernel patch went with user tool v1 version.
The user tool v2 version did a little modification according to the final
kernel patch. The only difference is not to mandate SAMPLE_ADDR
when SAMPLE_PHYS_ADDR.

Thanks,
Kan
 
> 
> >This patch is kernel patch.
> >The user space patch can be found here.
> >https://urldefense.proofpoint.com/v2/url?u=https-
> 3A__www.spinics.net_lists_kernel_msg2587093.html&d=DwIBaQ&c=jf_iaSHv
> JObTbx-siA1ZOg&r=3f2W2m24mqGnx1C8qDsVjM_Sd89MwbaDB37IJVL-
> h7w&m=bL7qsJKf8aRpvBVr07ODZxoQhPgxffpGFgN9A4iyACw&s=R1OMYJt1sz
> qNhPZu8QQDDRCnQgHZiQzcCPzofF6FIF8&e=
> 
> Maddy
> 
> 
> 
> Thanks maddy!
>