loadtimezone and n_sec impl is slow in starrocks

[aaawuanjun]

other olap use cctz, it occure 2 function inside cctz
n_sec and loadTimeZone
it calls too much time, so kernel goes the spin_lock_slowpath

[devbww]

I'm afraid your report lacks enough context so as to render it unactionable.

If you believe any CCTZ functions are doing unnecessary work, or have ideas about optimizations, please submit your detailed thoughts. Thanks.

[aaawuanjun]

First, change normal lock to readwrite lock in LoadTimeZone method

[aaawuanjun]

about read write lock, see pull #214

before modify, lock has race condition
online information:

test env information:

after this, lock's hot will decrease
test env information:

brpc's lock info inside LoadTimeZone will down

[aaawuanjun]

what's the period of new version comes out?