On 17.05.2012 06:43, Robert Haas wrote:
The attached patch provides some rough instrumentation for determining
where palloc calls are coming from. This is obviously just for
noodling around with, not for commit, and there may well be bugs. But
enjoy.
I gave this a quick spin on a couple of test workloads: a very short
pgbench test, a very short pgbench -S test, and the regression tests.
On the pgbench test, the top culprits are ExecInitExpr() and
expression_tree_mutator(); in both cases, the lappend() call for the
T_List case is the major contributor. Other significant contributors
include _copyVar(), which I haven't drilled into terribly far but
seems to be coming mostly from add_vars_to_targetlist();
buildRelationAliases() via lappend, pstrdup, and makeString;
ExecAllocTupleTableSlot(); and makeColumnRef() via makeNode, lcons,
and makeString.
What percentage of total CPU usage is the palloc() overhead in these
tests? If we could totally eliminate the palloc() overhead, how much
faster would the test run?
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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