Re: [PATCH 1/3] perf report: Fix OOM error in TUI mode on s390

On 5/22/19 8:08 PM, Arnaldo Carvalho de Melo wrote:

Em Wed, May 22, 2019 at 04:45:59PM +0200, Thomas Richter escreveu:

.....

quoted

This size kills the TUI interface when executing the following
code:

  process_sample_event()
    hist_entry_iter__add()
      hist_iter__report_callback()
        hist_entry__inc_addr_samples()
          symbol__inc_addr_samples(symbol = __bss_stop)
            symbol__cycles_hist()
               annotated_source__alloc_histograms(...,
				                symbol__size(sym),
		                                ...)

This function allocates memory to save sample histograms.
The symbol_size() marco is defined as sym->end - sym->start, which
results in above value of 0x3fe6e64a850 bytes and
the call to calloc() in annotated_source__alloc_histograms() fails.

Humm, why are we getting samples in that area? Is it some JITted thing
like BPF? What is it?

Why not just not consider the calloc failure as fatal, and when/if the
user asks for annotation on such symbol, tell the user that it wasn't
possible to allocate N bytes for it?

- Arnaldo

I have not debugged why this sample address was recorded. BPF code was not
running.

I have no problem with making calloc() failure no fatal, however we might
still allocate large memory...

I will send a new patch.

-- 
Thomas Richter, Dept 3252, IBM s390 Linux Development, Boeblingen, Germany
--
Vorsitzender des Aufsichtsrats: Matthias Hartmann
Geschäftsführung: Dirk Wittkopp
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