I used an Segmented steel Sleeve Armored cable lock made for Specialized, It coils up small ..
and I made a top tube fitting mount for the down tube bracket, as I have Water bottles on the other 2 tubes.
Plus I carry a second long thin cable to lock the bike to stuff in camp, trees, picnic benches etc.

Newer Bike I have an AXA Defender ring lock fixed to the frame, its on the front side of the seatstays.
they make a chain that plugs into the ring lock, and with the 1.4M length version of that I can lock up my front wheel,
and run the chain around some stuff, still bring another cable a bit thicker, also, to lock up to stuff I cannot get that,
lock-up chain thru or around, that's in town, as a commuter, on tour I'd still bring the 10' long thin cable too..

Advantage to the Frame mounted Ring lock it is always there, so, just by closing that and removing the key,
you can keep the bike from being rolled/ridden off.

no temptation to say "it'll be OK I'm just going in for a second", because you packed the lock too far in the bags
to be instantly convenient.
Abus makes a ring lock and lockup chain thing too, now, if Dutch AXA is not distributed to Korea, can alway be posted from EU dealer..


another Abus product, one of their link locks ,
is what I got for my Bike Friday, it folds up to go in a holster,
that straps onto the frame, in mycase hangs below the down tube.


I with it, lock my frame to the fixed object,
and loop a cable thru both wheels.