manipulate session cache size
SSL_CTX_sess_set_cache_size(SSL_CTX *ctx, long t);long
SSL_CTX_sess_set_cache_size(SSL_CTX *ctx, long t);
SSL_SESSION_CACHE_MAX_SIZE_DEFAULT, currently 1024×20, so that up to 20000 sessions can be held. This size can be modified using the SSL_CTX_sess_set_cache_size() call. A special case is the size 0, which is used for unlimited size.When the maximum number of sessions is reached, no more new sessions are added to the cache. New space may be added by calling SSL_CTX_flush_sessions(3) to remove expired sessions.If the size of the session cache is reduced and more sessions are already in the session cache, old session will be removed the next time a session shall be added. This removal is not synchronized with the expiration of sessions.