Unstable test session_test.go:5721: testTiDBAsLibrary.TestMemoryLeak

[zhouqiang-cl]

Bug Report

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[2021-09-26T01:30:14.688Z] FAIL: session_test.go:5721: testTiDBAsLibrary.TestMemoryLeak

[2021-09-26T01:30:14.688Z] 

[2021-09-26T01:30:14.688Z] session_test.go:5744:

[2021-09-26T01:30:14.688Z]     c.Assert(memStat.HeapInuse-oldHeapInUse, Less, uint64(150*units.MiB))

[2021-09-26T01:30:14.688Z] ... compare_one uint64 = 0xaa24000

[2021-09-26T01:30:14.688Z] ... compare_two uint64 = 0x9600000

1. Minimal reproduce step (Required)

in ci https://ci.pingcap.net/blue/organizations/jenkins/tidb-unit-test-nightly/detail/tidb-unit-test-nightly/11379/pipeline

2. What did you expect to see? (Required)

3. What did you see instead (Required)

4. What is your TiDB version? (Required)

[zhouqiang-cl]

duplicate with #28348

[github-actions]

Please check whether the issue should be labeled with 'affects-x.y' or 'fixes-x.y.z', and then remove 'needs-more-info' label.