Re: Parser Cruft in gram.y

On Wed, Dec 19, 2012 at 10:18 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> valgrind comes with a tool called cachegrind which can emulate the
>> cache algorithm on some variants of various cpus and produce reports.
>> Can it be made to produce a report for a specific block of memory?
>
> I believe that oprofile can be persuaded to produce statistics about
> where in one's code are the most cache misses, not just the most
> wall-clock ticks; which would shed a lot of light on this question.
> However, my oprofile-fu doesn't quite extend to actually persuading it.

perf can certainly do this.

$ perf record -a -e cache-misses pgbench -n -S -T 30
...output elided...
$ perf report -d postgres | grep -v '^#' | head
     8.88%   postgres  base_yyparse
     7.05%    swapper  0x807c
     4.67%   postgres  SearchCatCache
     3.77%    pgbench  0x172dd58
     3.47%   postgres  hash_search_with_hash_value
     3.23%   postgres  AllocSetAlloc
     2.58%   postgres  core_yylex
     1.87%   postgres  LWLockAcquire
     1.83%   postgres  fmgr_info_cxt_security
     1.75%   postgres  0x4d1054

For comparison:

$ perf record -a -e cycles -d postgres pgbench -n -S -T 30
$ perf report -d postgres | grep -v '^#' | head
     6.54%     postgres  AllocSetAlloc
     4.08%      swapper  0x4ce754
     3.60%     postgres  hash_search_with_hash_value
     2.74%     postgres  base_yyparse
     2.71%     postgres  MemoryContextAllocZeroAligned
     2.57%     postgres  MemoryContextAlloc
     2.36%     postgres  SearchCatCache
     2.10%     postgres  _bt_compare
     1.70%     postgres  LWLockAcquire
     1.54%     postgres  FunctionCall2Coll

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
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