performance regression after update to the newest master commit

[glorv]

Describe the bug
Recent I was trying to update the grpcio version from v0.10.4 to the newest master commit for tikv. And when I did some benchmark using sysbench I found there are performance regression within different workloads(oltp_read_only, oltp_read_write and oltp_write_only), the qps dropped around 5% ~ 10%.
The v0.10.4 build is based on commit: tikv/tikv@966e134
The master build is based on: https://github.com/glorv/tikv/commits/grpc-master/

From the metrics I saw master grpc threads consumed more cpu time than v0.10.4:

From the cpu profiling, I saw the cq_next call consumed more cpu time while other part are almost the same:
(v0.10.4)

(master)

With v0.10.4, grpc cost about 14.78% of all cpu time:
CallTag::resolve(4.12%), CompletionQueue::next(1.45%), UnfinishedWork::finish(9.22%)

With master commit, gRPC cost about 21.35% of all cpu time:
CallTag::resolve(5.87%), CompletionQueue::next(4.77%), UnfinishedWork::finish(10.71%)

It seems that some changes in CompletionQueue may be the root cause of this regression.
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Expected behavior
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System information

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[glorv]

/cc @Connor1996 @overvenus @LykxSassinator @SpadeA-Tang
Please help take a look if you have any ideas

[glorv]

Seems this is duplicated with #643