store/copr: set a smaller channel size for coprocessor task in the keep order case

[tiancaiamao]

What problem does this PR solve?

Issue Number: close #36041

Problem Summary:

What is changed and how it works?

Channel size 128 is too large and in select ... order by _tidb_rowid query, a lot of coprocessor response packet
is cached in the channel, consume much more memory than necessary.

Set a smaller channel size, the performance is basically the same ... the memory usage reduce dramatically

Channel size = 16
time mysql -h 127.0.0.1 -u root -P 4000 -B ens_rb -e 'set @@tidb_enable_paging = 1; select * FROM `ens_rb003`.`rb_acct_int_detail` order by _tidb_rowid' > /dev/null
real        2m2.946s
user        0m58.253s
sys        0m4.552s

Channel size = 128
genius@genius-System-Product-Name:~/project/src/github.com/pingcap/tidb$ time mysql -h 127.0.0.1 -u root -P 4000 -B ens_rb -e 'set @@tidb_enable_paging = 1; select * FROM `ens_rb003`.`rb_acct_int_detail` order by _tidb_rowid' > /dev/null
real        1m57.945s
user        0m57.367s
sys        0m4.701s

Channel size = 18
genius@genius-System-Product-Name:~/project/src/github.com/pingcap/tidb$ time mysql -h 127.0.0.1 -u root -P 4000 -B ens_rb -e 'set @@tidb_enable_paging = 1; select * FROM `ens_rb003`.`rb_acct_int_detail` order by _tidb_rowid' > /dev/null
real        1m59.419s
user        0m57.893s
sys        0m4.581s

Channel size = 2~8 takes 2min25 ~2min30, although memory usage is low, performance decrease b.t.w

Check List

Tests

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

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

Please refer to Release Notes Language Style Guide to write a quality release note.

Set a smaller channel size for coprocessor task, in the full table scan 'order by' case, this change can reduce memory usage for the coprocessor paging protocol.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• XuHuaiyu
• wshwsh12

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[sre-bot]

Code Coverage Details: https://codecov.io/github/pingcap/tidb/commit/4d4b58d6900e7945bf4d909da710533fb78fb9e1

[tiancaiamao]

/merge

[ti-chi-bot]

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

Commit hash: 90caf8c

[sre-bot]

TiDB MergeCI notify

✅ Well Done! New fixed [1] after this pr merged.

CI Name	Result	Duration	Compare with Parent commit
idc-jenkins-ci/integration-cdc-test	✅ all 36 tests passed	24 min	Fixed
idc-jenkins-ci-tidb/integration-common-test	🟢 all 11 tests passed	24 min	Existing passed
idc-jenkins-ci-tidb/common-test	🟢 all 12 tests passed	13 min	Existing passed
idc-jenkins-ci-tidb/integration-ddl-test	🟢 all 6 tests passed	7 min 39 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-2	🟢 all 28 tests passed	6 min 45 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-1	🟢 all 26 tests passed	6 min 30 sec	Existing passed
idc-jenkins-ci-tidb/tics-test	🟢 all 1 tests passed	5 min 32 sec	Existing passed
idc-jenkins-ci-tidb/integration-compatibility-test	🟢 all 1 tests passed	3 min 16 sec	Existing passed
idc-jenkins-ci-tidb/mybatis-test	🟢 all 1 tests passed	2 min 51 sec	Existing passed
idc-jenkins-ci-tidb/plugin-test	🟢 build success, plugin test success	4min	Existing passed