1. 12 May, 2016 5 commits
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  4. 09 May, 2016 1 commit
    • Chris Phlipot's avatar
      perf symbols: Fix handling of zero-length symbols. · 9c7b37cd
      Chris Phlipot authored
      This change introduces a fix to symbols__find, so that it is able to
      find symbols of length zero (where start == end).
      
      The current code has the following problem:
      
      - The current implementation of symbols__find is unable to find any symbols
        of length zero.
      
      - The db-export framework explicitly creates zero length symbols at
        locations where no symbol currently exists.
      
      The combination of the two above behaviors results in behavior similar
      to the example below.
      
      1. addr_location is created for a sample, but symbol is unable to be
         resolved.
      
      2. db export creates an "unknown" symbol of length zero at that address
         and inserts it into the dso.
      
      3. A new sample comes in at the same address, but symbol__find is unable
         to find the zero length symbol, so it is still unresolved.
      
      4. db export sees the symbol is unresolved, and allocated a duplicate
         symbol, even though it already did this in step 2.
      
      This behavior continues every time an address without symbol information
      is seen, which causes a very large number of these symbols to be
      allocated.
      
      The effect of this fix can be observed by looking at the contents of an
      exported database before/after the fix (generated with
      scripts/python/export-to-postgresql.py)
      
      Ex.
      BEFORE THE CHANGE:
      
        example_db=# select count(*) from symbols;
         count
        --------
         900213
        (1 row)
      
        example_db=# select count(*) from symbols where symbols.name='unknown';
         count
        --------
         897355
        (1 row)
      
        example_db=# select count(*) from symbols where symbols.name!='unknown';
         count
        -------
          2858
        (1 row)
      
      AFTER THE CHANGE:
      
        example_db=# select count(*) from symbols;
         count
        -------
         25217
        (1 row)
      
        example_db=# select count(*) from symbols where name='unknown';
         count
        -------
         22359
        (1 row)
      
        example_db=# select count(*) from symbols where name!='unknown';
         count
        -------
          2858
        (1 row)
      Signed-off-by: default avatarChris Phlipot <cphlipot0@gmail.com>
      Cc: Adrian Hunter <adrian.hunter@intel.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Link: http://lkml.kernel.org/r/1462612620-25008-1-git-send-email-cphlipot0@gmail.com
      [ Moved the test to later in the rb_tree tests, as this not the likely case ]
      Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
      9c7b37cd