Method PurgeCache

library/cpp/neh/https.cpp:590–628

            }

            void PurgeCache() noexcept {
                //try remove at least ExceedSoftLimit() oldest connections from cache
                //вычисляем долю кеша, которую нужно почистить (в 256 долях) (но не менее 1/32 кеша)
                const size_t frac256 = Min<size_t>(256, Max<size_t>(8, (ExceedSoftLimit() << 8) / (CachedConnections.Val() + 1)));
                TConnectionRef tmp;

                for (size_t i = 0; i < MaxConnId_.load(std::memory_order_acquire) && !Shutdown_; i++) {
                    TConnList& tc = Lst_.Get(i);
                    if (size_t qsize = tc.Size()) {
                        //в каждой очереди чистим вычисленную долю
                        size_t purgeCounter = ((qsize * frac256) >> 8);

                        if (!purgeCounter && qsize) {
                            if (qsize == 1) {
                                // check lifeness
                                TConnectionRef res;
                                if (tc.Dequeue(&res)) {
                                    // if connection valid put it back
                                    if (IsNotSocketClosedByOtherSide((*res)->Fd()) && !(*res)->ShutdownReceived()) {
                                        tc.Enqueue(res);
                                    } else {
                                        ActiveConnections.Inc();
                                        CachedConnections.Dec();
                                    }
                                }
                            } else {
                                // drop at least one connection from queue with at least 2 connections
                                purgeCounter = 1;
                            }
                        }

                        while (purgeCounter-- && tc.Dequeue(&tmp)) {
                            ActiveConnections.Inc();
                            CachedConnections.Dec();
                            tmp->Reset(nullptr);
                        }
                    }
                }
            }

            inline TConnList& ConnList(const TResolvedHost& addr) {
                return Lst_.Get(addr.Id);