Optimize reload-zones logic to reduce thread scheduling times

[zjs604381586]

Short description

When reload-zones sets thread local variables, it aggregates two operations into one thread scheduling, and completes the setting of two variables in one function. Because both functions return nullptr, no memory leak occurs.

Checklist

I have:

• read the CONTRIBUTING.md document
• compiled this code
• tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)
• checked that this code was merged to master

[coveralls]

Pull Request Test Coverage Report for Build 16615247828

Details

• 4 of 4 (100.0%) changed or added relevant lines in 1 file are covered.
• 48 unchanged lines in 12 files lost coverage.
• Overall coverage decreased (-0.03%) to 65.845%

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Files with Coverage Reduction	New Missed Lines	%
pdns/iputils.hh	1	78.76%
ext/json11/json11.cpp	2	62.65%
pdns/dnsdistdist/dnsdist-crypto.cc	2	75.72%
pdns/misc.cc	2	60.2%
pdns/sstuff.hh	2	57.14%
pdns/dnsdistdist/dnsdist-carbon.cc	3	62.33%
pdns/stubresolver.cc	3	77.02%
pdns/recursordist/lwres.cc	5	70.84%
pdns/dnsdistdist/dnsdist-tcp.cc	6	77.14%
pdns/remote_logger.cc	6	55.36%

Totals
Change from base Build 16614910507:	-0.03%
Covered Lines:	127942
Relevant Lines:	165732

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💛 - Coveralls

[omoerbeek]

Do you have any measurements it makes a real difference?

[zjs604381586]

Do you have any measurements it makes a real difference?

I don't have actual test data. I understand that resetting two variables in one epoll schedule will definitely improve performance compared to scheduling twice.