store/copr: use non-buffered channel for coprocessor response

[tiancaiamao]

What problem does this PR solve?

Issue Number: close #35987

Problem Summary:

What is changed and how it works?

DistSQL concurrency default value is 16, there are so many workers already.
If we use a buffered channel for the tasks, there will be a lot of data cached in TiDB, consuming a lot of memory.

Change the buffered channel to a non-buffered channel, to reduce the memory footprint.

Note, this change does not make performance regression!

Before

time mysql -h 127.0.0.1 -u root -P 4000 -B ens_rb -e 'set @@tidb_enable_paging = 1; select * from ens_rb.fm_acct_client_relation' > /dev/null

real	2m32.304s
user	1m36.585s
sys	0m7.636s

After

time mysql -h 127.0.0.1 -u root -P 4000 -B ens_rb -e 'set @@tidb_enable_paging = 1; select * from ens_rb.fm_acct_client_relation' > /dev/null

real	2m29.395s
user	1m34.884s
sys	0m7.640s

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.

Use non-buffered channel for coprocessor worker, this change dramatically reduce the memory usage in the full table scan scenario.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• XuHuaiyu
• wshwsh12

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[tiancaiamao]

Also close #34849

[tiancaiamao]

/merge

[ti-chi-bot]

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

Commit hash: 11068ad

[tiancaiamao]

/run-unit-test

[tiancaiamao]

/run-all-tests

[tiancaiamao]

/run-unit-test
/run-mysql-test

[tiancaiamao]

/run-mysql-test
/run-unit-test

[hawkingrei]

/run-unit-test
/run-check_dev_2

[tiancaiamao]

/run-unit-test

[tiancaiamao]

/run-check_dev_2

[tiancaiamao]

/run-unit-test

[tiancaiamao]

/hold

[tiancaiamao]

/unhold

After #36242 it should work now.

[sre-bot]

Code Coverage Details: https://codecov.io/github/pingcap/tidb/commit/5140c8d3dba4f559834c51b62bfd7d0e77551abd

[sre-bot]

TiDB MergeCI notify

🔴 Bad News! [1] CI still failing after this pr merged.
These failed integration tests don't seem to be introduced by the current PR.

CI Name	Result	Duration	Compare with Parent commit
idc-jenkins-ci-tidb/tics-test	🔴 failed 1, success 0, total 1	54 sec	Existing failure
idc-jenkins-ci-tidb/integration-common-test	🟢 all 11 tests passed	25 min	Existing passed
idc-jenkins-ci/integration-cdc-test	🟢 all 36 tests passed	25 min	Existing passed
idc-jenkins-ci-tidb/common-test	🟢 all 12 tests passed	15 min	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-1	🟢 all 26 tests passed	6 min 21 sec	Existing passed
idc-jenkins-ci-tidb/integration-ddl-test	🟢 all 6 tests passed	6 min 2 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-2	🟢 all 28 tests passed	5 min 25 sec	Existing passed
idc-jenkins-ci-tidb/mybatis-test	🟢 all 1 tests passed	3 min 3 sec	Existing passed
idc-jenkins-ci-tidb/integration-compatibility-test	🟢 all 1 tests passed	2 min 52 sec	Existing passed
idc-jenkins-ci-tidb/plugin-test	🟢 build success, plugin test success	4min	Existing passed