Any projects which want to use Hush code from now on will need to be licensed as
GPLv3 or we will send the lawyers: https://www.softwarefreedom.org/
Notably, Komodo (KMD) is licensed as GPLv2 and is no longer compatible to receive
code changes, without causing legal issues. MIT projects, such as Zcash, also cannot pull
in changes from the Hush Full Node without permission from The Hush Developers,
which may in some circumstances grant an MIT license on a case-by-case basis.
ZEC took the route of disabling this by default, so debug.log files grow without limit,
in attempt to gather more data about CVE-2019-16930, which was fixed in the same emergency
release as changing this default behavior.
KMD has chosen to ignore that ZEC change, which I find reasonable. We take the middle path,
and 10X increase the size limit.
Now debug.log must hit 100MB to be resized, and potentially lose some data about attacks.
To determine the default for `-par`, the number of script verification
threads, use [boost:🧵:physical_concurrency()](http://www.boost.org/doc/libs/1_58_0/doc/html/thread/thread_management.html#thread.thread_management.thread.physical_concurrency)
which counts only physical cores, not virtual cores.
Virtual cores are roughly a set of cached registers to avoid context
switches while threading, they cannot actually perform work, so spawning
a verification thread for them could even reduce efficiency and will put
undue load on the system.
Should fix issue #6358, as well as some other reported system overload
issues, especially on Intel processors.
The function was only introduced in boost 1.56, so provide a utility
function `GetNumCores` to fall back for older Boost versions.
Duke Leto
Jonathan "Duke" Leto