Each preprocessing worker rewrites history upon completion, this results in behaviour when one worker allocates history and then the other frees history and allocates new.

Expected:
For best performance threads should avoid freeing memory allocated by other threads, especially because it is redundant to always rewrite history, since in many cases with javascript and throttling it might not change for long time.

Steps:
Send 1000 values each 1 MB and javascript that sleeps 50 milliseconds, notice that memory is not released back to system with glibc, add macro to javascript and notice that since there is no more history then memory is released.