linux-kernel - Re: [PATCH v2] perf tools: allow map files to specify DSO

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Message-ID: <e6272e7c-25fd-0d2d-4199-fcf3ec604546@akamai.com>
Date:   Mon, 7 May 2018 14:30:32 -0700
From:   Josh Hunt <johunt@...mai.com>
To:     Andi Kleen <ak@...ux.intel.com>
Cc:     mingo@...hat.com, acme@...nel.org, peterz@...radead.org,
        alexander.shishkin@...ux.intel.com, jolsa@...hat.com,
        namhyung@...nel.org, wangnan0@...wei.com,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        eranian@...gle.com
Subject: Re: [PATCH v2] perf tools: allow map files to specify DSO

On 05/07/2018 11:40 AM, Andi Kleen wrote:
> On Mon, May 07, 2018 at 02:24:16PM -0400, Josh Hunt wrote:
>> Add the ability to specify a DSO in the /tmp/perf-<PID>.map file.
>> The DSO should be the first line in the file and readable by the
>> running user. If a valid DSO is found all other contents of the
>> file will be ignored. This allows things like callchain unwinding
>> with DWARF to work.
> 
> FWIW it's ok, but also obsolete with Kirill's large-pages-in-tmpfs
> work in newer kernels. With that you can just copy the executable into
> a 2MB tmpfs and disable the manual huge page copying and everything
> should work as usually.
> 
> So essentially it's only a hack for old kernels and old binaries.
> 
> But doesn't hurt I guess.

Ah, very interesting. I wasn't aware of this. Can you point me to some 
more details on this process?

Thanks
Josh