The debug.* sysctl's that lack a description are as follows:

debug.if_fwe_debug:
debug.sbp_debug: SBP debug flag

debug.mddebug:

debug.ips.ignore_flush_cmd: Do not issue IPS_CACHE_FLUSH_CMD on BUF_CMD_FLUSH
debug.elf_legacy_coredump:
debug.elf_trace:
debug.boothowto:
debug.dev_refs:
debug.free_devt:
debug.fdexpand:
debug.sizeof.cdev: sizeof(struct cdev)
debug.sizeof.proc: sizeof(struct proc)
debug.sizeof.vnode: sizeof(struct vnode)
debug.sizeof.disk: sizeof(struct disk)
debug.sizeof.diskslices: sizeof(struct diskslices)
debug.sizeof.buf: sizeof(struct buf)
debug.use_malloc_pattern:
debug.bootverbose: Verbose kernel messages
debug.trace_on_panic: Print stack trace on kernel panic
debug.debugger_on_panic: Run debugger on kernel panic
debug.choose_affinity: chooseproc() was smart
debug.remote_resched_affinity: Number of remote rescheds
debug.remote_resched_nonaffinity: Number of remote rescheds
debug.scdebug:
debug.usched_optimal: acquire_curproc() was optimal
debug.usched_nonoptimal: acquire_curproc() was not optimal
debug.bsd4_runqcount:
debug.serialize_boround:
debug.serialize_boshift:
debug.serialize_bolimit:
debug.spin_test_count:
debug.spinlocks_bolim:
debug.spinlocks_contested2:
debug.spinlocks_contested1:
debug.rman_debug: rman debug
debug.ttydebug:
debug.disablefullpath:
debug.disablecwd:
debug.ncsize:
debug.vnsize:
debug.numdefered:
debug.nclockwarn:
debug.ncnegfactor:
debug.nchash:
debug.ncvp_debug:
debug.numvnodes:
debug.wantfreevnodes:
debug.freevnodes:
debug.vnlru_nowhere: Number of times the vnlru process ran without success
debug.rush_requests:
debug.bpf_maxbufsize:
debug.bpf_bufsize:
debug.if_tun_debug:
debug.ncr_debug:
debug.dir_entry:
debug.direct_blk_ptrs:
debug.inode_bitmap:
debug.indir_blk_ptrs:
debug.sync_limit_hit:
debug.ino_limit_hit:
debug.blk_limit_hit:
debug.ino_limit_push:
debug.blk_limit_push:
debug.worklist_push:
debug.tickdelay:
debug.max_softdeps:
debug.dircheck:
debug.crypto_timing: Enable/disable crypto timing support
debug.apm_debug:
debug.minidump: Enable mini crash dumps
debug.timer_warn:

Research these sysctl's in the kernel code and document each with a descriptive but concise sentence (approximately 3-15 words).

Deliverables: A description of each sysctl listed above.

Bonus deliverables: The above descriptions in the form of a kernel patch