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gc_worker: reduce GC scan locks when meeting region cache miss (#18385) #18876

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merged 1 commit into from
Jul 30, 2020

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cherry-pick #18385 to release-4.0


What problem does this PR solve?

Issue Number: close #xxx

Problem Summary:

currently, gc worker will rescan locks when meet region cache miss error which makes slow scan job become more slow.

What is changed and how it works?

What's Changed, How it Works:

when region cache miss error(current is a fake epochNotMatch), it just indicates "maybe region has changed and we need to reload region from PD", we can continue resolve scan lock result if all lock still in that region.

this can help situations like:

  • lock and region hasn't changed but region cache expired
  • lock's region's key range didn't change but maybe add new peer(id is same but confVer or ver changed)
  • all lock has changed from region A to region B

but it didn't help the situation that:

  • lock's region has been split into two region

maybe we can improve it later(to avoid complex modification)

Related changes

  • Need to cherry-pick to the release branch

Check List

Tests

  • Unit test
  • Integration test
  • Manual test (add detailed scripts or steps below)
  • No code

Side effects

  • n/a

Release note

  • Reduce GC scan locks when meeting region cache miss

This change is Reviewable

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/run-all-tests

@ti-srebot ti-srebot added the status/LGT1 Indicates that a PR has LGTM 1. label Jul 30, 2020
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LGTM

@ti-srebot ti-srebot added status/LGT2 Indicates that a PR has LGTM 2. and removed status/LGT1 Indicates that a PR has LGTM 1. labels Jul 30, 2020
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jackysp commented Jul 30, 2020

/merge

@ti-srebot ti-srebot added the status/can-merge Indicates a PR has been approved by a committer. label Jul 30, 2020
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Your auto merge job has been accepted, waiting for:

  • 18529

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jackysp commented Jul 30, 2020

/run-unit-test

@jackysp jackysp merged commit 6055d8b into pingcap:release-4.0 Jul 30, 2020
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4 participants