From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH bpf-next 2/3] bpf: emit RECORD_MMAP events for bpf prog
 load/unload
Date: Thu, 20 Sep 2018 15:56:51 +0200
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Cc: Alexei Starovoitov <ast@kernel.org>,
        "David S . Miller" <davem@davemloft.net>, daniel@iogearbox.net,
        netdev@vger.kernel.org, kernel-team@fb.com
To: Arnaldo Carvalho de Melo <acme@kernel.org>
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On Thu, Sep 20, 2018 at 10:25:45AM -0300, Arnaldo Carvalho de Melo wrote:
> PeterZ provided a patch introducing PERF_RECORD_MUNMAP, went nowhere due
> to having to cope with munmapping parts of existing mmaps, etc.
> 
> I'm still more in favour of introduce PERF_RECORD_MUNMAP, even if for
> now it would be used just in this clean case for undoing a
> PERF_RECORD_MMAP for a BPF program.
> 
> The ABI is already complicated, starting to use something called
> PERF_RECORD_MMAP for unmmaping by just using a NULL name... too clever,
> I think.

Agreed, the PERF_RECORD_MUNMAP patch was fairly trivial, the difficult
part was getting the perf tool to dtrt for that use-case. But if we need
unmap events, doing the unmap record now is the right thing.