kvflowcontroller: mutex contention #105508
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Perf of queries or internals. Solution not expected to change functional behavior.
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erikgrinaker
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irfansharif
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Fixes cockroachdb#105508. Release note: None
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Clawed back the throughput loss with #106466. 
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irfansharif
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Aug 21, 2023
Fixes cockroachdb#105508. Under kv0/enc=false/nodes=3/cpu=96 we observed significant mutex contention on kvflowcontroller.Controller.mu. We were using a single mutex to adjust flow tokens across all replication streams. There's a natural sharding available here - by replication stream - that eliminates the contention and fixes the throughput drop. The kv0 test surfaced other performance optimizations (mutex contention, allocated objects, etc.) that we'll address in subsequent PRs. Release note: None
craig bot
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108444: plpgsql: add support for WHILE loops r=mgartner a=mgartner
#### plpgsql/parser: parse WHILE loops
Release note: None
#### opt: support PL/pgSQL WHILE loops
This commit adds support for PL/pgSQL `WHILE` loops. A `WHILE` loop is
syntactic sugar for a `LOOP` with that exits conditionally, so we build
a `WHILE` loop with a simple transformation:
WHILE [cond] LOOP
[body];
END LOOP;
=>
LOOP
IF [cond] THEN
[body];
ELSE
EXIT;
END IF;
END LOOP;
This transformation allows us to avoid adding complicated logic
specifically for `WHILE` loops and instead rely on the existing
implementations for `LOOP` and `IF/ELSE` statements.
Epic: CRDB-799
Release note: None
#### opt: add unimplemented errors for EXIT/CONTINUE WHEN
Release note: None
109170: kvflowcontroller: eliminate mutex contention r=irfansharif a=irfansharif
Fixes #105508.
Under kv0/enc=false/nodes=3/cpu=96 we observed significant mutex contention on kvflowcontroller.Controller.mu. We were using a single mutex to adjust flow tokens across all replication streams. There's a natural sharding available here - by replication stream - that eliminates the contention and fixes the throughput drop.
The kv0 test surfaced other performance optimizations (mutex contention, allocated objects, etc.) that we'll address in subsequent PRs.
Release note: None
Co-authored-by: Marcus Gartner <[email protected]>
Co-authored-by: irfan sharif <[email protected]>
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kv0/enc=false/nodes=3/cpu=96is showing significant mutex contention onkvflowcontroller.Controller.mu:This is possibly the cause of a significant performance regression on this benchmark:
Jira issue: CRDB-29088
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