There are some potential feefilter cleanups mentioned and motivated in comment https://github.com/bitcoin/bitcoin/pull/21509#issuecomment-805808485 . If you address the locking one, please be careful and make sure that `round()` is only called under a lock. See https://github.com/bitcoin/bitcoin/pull/21509#issuecomment-807992199

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static const bool DEFAULT_REST_ENABLE = false;
#ifdef WIN32
#define MIN_CORE_FILEDESCRIPTORS 0
#else
#define MIN_CORE_FILEDESCRIPTORS 150
#endif
static const char* DEFAULT_ASMAP_FILENAME="ip_asn.map";
/**
 * The PID file facilities.
 */
static const char* BITCOIN_PID_FILENAME = "bitcoind.pid";
static fs::path GetPidFile(const ArgsManager& args)
{
    return AbsPathForConfigVal(fs::path(args.GetArg("-pid", BITCOIN_PID_FILENAME)));
}
[[nodiscard]] static bool CreatePidFile(const ArgsManager& args)
{
    fsbridge::ofstream file{GetPidFile(args)};
    if (file) {
#ifdef WIN32
        tfm::format(file, "%d\n", GetCurrentProcessId());
#else
        tfm::format(file, "%d\n", getpid());
#endif
        return true;
    } else {
        return InitError(strprintf(_("Unable to create the PID file '%s': %s"), GetPidFile(args).string(), std::strerror(errno)));
    }
}
void Interrupt(NodeContext& node)