Mostafa Mokhtar created IMPALA-6744:
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Summary: Inline codegend_compare_fn_ to avoid per row memory loads and function call
Key: IMPALA-6744
URL: https://issues.apache.org/jira/browse/IMPALA-6744
Project: IMPALA
Issue Type: Bug
Components: Backend
Affects Versions: Impala 2.13.0
Reporter: Mostafa Mokhtar
Assignee: Tianyi Wang
Attachments: percentile query profile.txt
While evaluating Sort performance I noticed that the codegened compare function is not inlined which results in large overhead per row.
Expected speedup is 10-15%
{code}
/// Returns a negative value if lhs is less than rhs, a positive value if lhs is
/// greater than rhs, or 0 if they are equal. All exprs (ordering_exprs_lhs_ and
/// ordering_exprs_rhs_) must have been prepared and opened before calling this,
/// i.e. 'sort_key_exprs' in the constructor must have been opened.
int ALWAYS_INLINE Compare(const TupleRow* lhs, const TupleRow* rhs) const {
return codegend_compare_fn_ == NULL ?
CompareInterpreted(lhs, rhs) :
(*codegend_compare_fn_)(ordering_expr_evals_lhs_.data(),
ordering_expr_evals_rhs_.data(), lhs, rhs);
}
{code}
From Perf
{code}
│ bool Sorter::TupleSorter::Less(const TupleRow* lhs, const TupleRow* rhs) { ▒
7.43 │ push %rbp ▒
3.23 │ mov %rsp,%rbp ▒
9.44 │ push %r12 ▒
2.69 │ push %rbx ▒
3.89 │ mov %rsi,%r12 ▒
2.98 │ mov %rdi,%rbx ▒
6.06 │ sub $0x10,%rsp ◆
│ --num_comparisons_till_free_; ▒
│ DCHECK_GE(num_comparisons_till_free_, 0); ▒
│ if (UNLIKELY(num_comparisons_till_free_ == 0)) { ▒
3.75 │ subl $0x1,0x18(%rdi) ▒
9.42 │ ↓ je 58 ▒
│ parent_->expr_results_pool_.Clear(); ▒
│ num_comparisons_till_free_ = state_->batch_size(); ▒
│ } ▒
│ return comparator_.Less(lhs, rhs); ▒
1.09 │17: mov 0x10(%rbx),%rdi ▒
│ /// Returns a negative value if lhs is less than rhs, a positive value if lhs is ▒
│ /// greater than rhs, or 0 if they are equal. All exprs (ordering_exprs_lhs_ and ▒
│ /// ordering_exprs_rhs_) must have been prepared and opened before calling this, ▒
│ /// i.e. 'sort_key_exprs' in the constructor must have been opened. ▒
│ int ALWAYS_INLINE Compare(const TupleRow* lhs, const TupleRow* rhs) const { ▒
│ return codegend_compare_fn_ == NULL ? ▒
2.69 │ mov 0x58(%rdi),%rax ▒
│ CompareInterpreted(lhs, rhs) : ▒
│ (*codegend_compare_fn_)(ordering_expr_evals_lhs_.data(), ▒
│ ordering_expr_evals_rhs_.data(), lhs, rhs); ▒
5.43 │ test %rax,%rax ▒
│ ↓ je 40 ▒
6.85 │ mov 0x20(%rdi),%rsi ▒
0.86 │ mov %rdx,%rcx ▒
2.55 │ mov 0x8(%rdi),%rdi ▒
3.38 │ mov %r12,%rdx ▒
6.10 │ → callq *(%rax) ▒
│ } ▒
5.84 │ add $0x10,%rsp ▒
│ /// All exprs (ordering_exprs_lhs_ and ordering_exprs_rhs_) must have been prepared ▒
│ /// and opened before calling this. ▒
│ /// Force inlining because it tends not to be always inlined at callsites, even in ▒
│ /// hot loops. ▒
│ bool ALWAYS_INLINE Less(const TupleRow* lhs, const TupleRow* rhs) const { ▒
│ return Compare(lhs, rhs) < 0; ▒
1.77 │ shr $0x1f,%eax ▒
7.91 │ pop %rbx ▒
4.11 │ pop %r12 ▒
0.49 │ pop %rbp ▒
1.75 │ ← retq ▒
│ /// i.e. 'sort_key_exprs' in the constructor must have been opened. ▒
│ int ALWAYS_INLINE Compare(const TupleRow* lhs, const TupleRow* rhs) const { ▒
│ return codegend_compare_fn_ == NULL ? ▒
│ CompareInterpreted(lhs, rhs) : ▒
│ (*codegend_compare_fn_)(ordering_expr_evals_lhs_.data(), ▒
│ ordering_expr_evals_rhs_.data(), lhs, rhs); ▒
│40: mov %r12,%rsi ▒
│ → callq impala::TupleRowComparator::CompareInterpreted(impala::TupleRow const*, impala::TupleRow const*) const ▒
│ add $0x10,%rsp ▒
│ /// All exprs (ordering_exprs_lhs_ and ordering_exprs_rhs_) must have been prepared ▒
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