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Change mark_cache size calculation to cut down memory usage #6861

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merged 6 commits into from
Mar 10, 2023

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hongyunyan
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@hongyunyan hongyunyan commented Feb 20, 2023

What problem does this PR solve?

Issue Number: close #7144

Problem Summary:

What is changed and how it works?

Currently, we calculate the mark_cache memory usage with marks.size() * sizeof(MarkInCompressedFile);
However, PODArray will do roundUpToPowerOfTwoOrZero when allocate element memory usage.
Thus, the memory usage is quite bigger then the calculation ways, which is close in twice time of the calculation ways.
To ensure the mark_cache only use the memory as we allocate, we change the memory usage calculation approach.

Then, we take the memory of allocation for MarkInCompressedFile for consideration. I think when we just initialization MarkInCompressedFile with the element number, we don't need to make the memory roundUpToPowerOfTwoOrZero. Thus, we change the alloc in PODArray(size n), to cut down the usage.

Check List

Tests

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

I compare the cluster with master tiflash and tiflash of this PR, to run a typical Workload.
We can find for the master tiflash, the memory will reach 13.0GB steeply and then continue slowing growth.
While for the tilfash of this PR, the memory will reach 11.5GB steeply and then continue slowing growth.
Thus, in a typical workload, we can cut down nearly 1.5GB.

image
image

Side effects

  • Performance regression: Consumes more CPU
  • Performance regression: Consumes more Memory
  • Breaking backward compatibility

Documentation

  • Affects user behaviors
  • Contains syntax changes
  • Contains variable changes
  • Contains experimental features
  • Changes MySQL compatibility

Release note

Reduce the resident memory usage of mark_cache.

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ti-chi-bot commented Feb 20, 2023

[REVIEW NOTIFICATION]

This pull request has been approved by:

  • breezewish
  • flowbehappy

To complete the pull request process, please ask the reviewers in the list to review by filling /cc @reviewer in the comment.
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@ti-chi-bot ti-chi-bot added release-note-none Denotes a PR that doesn't merit a release note. do-not-merge/work-in-progress Indicates that a PR should not merge because it is a work in progress. size/XS Denotes a PR that changes 0-9 lines, ignoring generated files. labels Feb 20, 2023
@hongyunyan hongyunyan marked this pull request as ready for review February 20, 2023 08:11
@ti-chi-bot ti-chi-bot removed the do-not-merge/work-in-progress Indicates that a PR should not merge because it is a work in progress. label Feb 20, 2023
@hongyunyan
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/run-all-tests

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/run-unit-test

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/run-all-tests

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/rebuild

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/run-all-tests

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/cc @breezewish @JaySon-Huang

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/run-sanitizer-test tsan

@@ -116,7 +116,7 @@ class PODArrayBase : private boost::noncopyable

void alloc_for_num_elements(size_t num_elements)
{
alloc(roundUpToPowerOfTwoOrZero(minimum_memory_for_elements(num_elements)));
alloc(minimum_memory_for_elements(num_elements));
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Plz add some comments to this method. About why don't we use roundUpToPowerOfTwoOrZero.

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LGTM with minor comments

@ti-chi-bot ti-chi-bot added the status/LGT1 Indicates that a PR has LGTM 1. label Mar 9, 2023
@ti-chi-bot ti-chi-bot added size/S Denotes a PR that changes 10-29 lines, ignoring generated files. release-note Denotes a PR that will be considered when it comes time to generate release notes. and removed size/XS Denotes a PR that changes 0-9 lines, ignoring generated files. release-note-none Denotes a PR that doesn't merit a release note. labels Mar 9, 2023
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The reduce of memory seems to be not as notable as expected. But anyway it's an improvement. Congrats!

@ti-chi-bot ti-chi-bot added status/LGT2 Indicates that a PR has LGTM 2. and removed status/LGT1 Indicates that a PR has LGTM 1. labels Mar 9, 2023
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/merge

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@hongyunyan: It seems you want to merge this PR, I will help you trigger all the tests:

/run-all-tests

You only need to trigger /merge once, and if the CI test fails, you just re-trigger the test that failed and the bot will merge the PR for you after the CI passes.

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This pull request has been accepted and is ready to merge.

Commit hash: 6a35dc2

@ti-chi-bot ti-chi-bot added the status/can-merge Indicates a PR has been approved by a committer. label Mar 10, 2023
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Reduce the memory usage of mark_cache
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