174     last_usage: Mutex<Instant>,  field
204     last_usage: Instant,  field
226             last_usage: Mutex::new(Instant::now()),  in new()
254             last_usage: *self.last_usage.lock().expect("In get_pruning_info."),  in get_pruning_info()
261     fn prune(&self, last_usage: Instant) -> Result<(), Error> {  in prune()
280         if *self.last_usage.lock().expect("In Operation::prune()") != last_usage {  in prune()
355         *self.last_usage.lock().expect("In touch.") = Instant::now();  in touch()
669                 last_usage: Instant,  in prune()  field
675                 |acc: Option<CandidateInfo>, &PruningInfo { last_usage, owner, index, forced }| {  in prune()
678                         .checked_duration_since(last_usage)  in prune()
686                                     Some(CandidateInfo { index, malus: 0, last_usage, age });  in prune()
690                                 Some(CandidateInfo { index, malus: 0, last_usage, age });  in prune()
713                                 Some(CandidateInfo { index, malus, last_usage, age })  in prune()
720                         Some(CandidateInfo { index: i, malus: m, last_usage: l, age: a }) => {  in prune()
722                                 Some(CandidateInfo { index, malus, last_usage, age })  in prune()
724                                 Some(CandidateInfo { index: i, malus: m, last_usage: l, age: a })  in prune()
735                 Some(CandidateInfo { index, malus: _, last_usage, age: _ }) => {  in prune()
738                             match op.prune(last_usage) {  in prune()