The problem with the film is that it is excessively true to the John le Carre' book, which was a slow read back in the day. I believe the hyper-fidelity was because le Carre' was involved in the filming.
Oldman as George Smiley spends most of the movie owlishly staring at people and things through his glasses, saying little and emoting even less. If you haven't read the book you'll think he does a terrible job, except that is how le Carre' wrote the Smiley character.
The film has little action, many flashbacks, an overall gloomy, smokey, depressive feel. The characters all smoke too much and lie to each other. If I didn't know different I'd think it was a Swedish film.
We purchased the DVD so I will watch it again a couple of times to sort out all the murky craziness. I like spy films but Tinker, Tailor isn't going to be one of my favorite films.