... to speed up processing if you have multiple CPU cores, use par=2 or par=3 to enable parallel validation threads, if your client permits it.
I don't think it's necessary to fiddle with this option. The default is
par=0 which means Bitcoin Core allocates automatically the number of threads for verification tasks. Depending on what other tasks your node device might have, a negative value for
par tells Core to leave that number of cores free for other processes than Core's.
# Set the number of script verification threads. (1 to CPU_CORES, 0 = automatic, less than 0 = leave that many cores free).
par=0
A reasonable value for
dbcache without inducing memory pressure to the system has likely a better effect on performance than trying to tweak the
par option.
Disclaimer: I've only played with
dbcache, never touched
par, so you should take my comments as an educated guess only.