I noticed that stunnel is constantly consuming 30% of one of my CPU cores. Looking at it with strace, I see that it is frequently (every 100 milliseconds?) waking up from a poll() system call, calling getpid() a couple of times and going back to sleep. [pid 3498] poll([{fd=6, events=POLLIN|POLLRDHUP}], 1, 100) = 0 (Timeout) [pid 3498] getpid() = 3494 [pid 3498] getpid() = 3494 [pid 3498] poll([{fd=6, events=POLLIN|POLLRDHUP}], 1, 100) = 0 (Timeout) [pid 3498] getpid() = 3494 [pid 3498] getpid() = 3494 [pid 3498] poll([{fd=6, events=POLLIN|POLLRDHUP}], 1, 100) = 0 (Timeout) [pid 3498] getpid() = 3494 [pid 3498] getpid() = 3494 [pid 3498] poll([{fd=6, events=POLLIN|POLLRDHUP}], 1, 100) = 0 (Timeout) [pid 3498] getpid() = 3494 [pid 3498] getpid() = 3494 AFAICT, this is a pipe that stunnel is using to talk to itself (maybe to communicate between threads)? # ls -l /proc/3498/fd total 0 lrwx------. 1 stunnel stunnel 64 Aug 23 10:12 0 -> /dev/null lrwx------. 1 stunnel stunnel 64 Aug 23 10:12 1 -> /dev/null lrwx------. 1 stunnel stunnel 64 Aug 23 10:12 10 -> 'socket:[37674]' lrwx------. 1 stunnel stunnel 64 Aug 23 10:12 11 -> 'socket:[37675]' lrwx------. 1 stunnel stunnel 64 Aug 23 10:12 12 -> 'socket:[37676]' lrwx------. 1 stunnel stunnel 64 Aug 23 10:12 2 -> /dev/null lr-x------. 1 stunnel stunnel 64 Aug 23 10:12 4 -> 'pipe:[38360]' l-wx------. 1 stunnel stunnel 64 Aug 23 10:12 5 -> 'pipe:[38360]' lr-x------. 1 stunnel stunnel 64 Aug 23 10:12 6 -> 'pipe:[38361]' l-wx------. 1 stunnel stunnel 64 Aug 23 10:12 7 -> 'pipe:[38361]' lrwx------. 1 stunnel stunnel 64 Aug 23 10:12 8 -> 'socket:[37672]' lrwx------. 1 stunnel stunnel 64 Aug 23 10:12 9 -> 'socket:[37673]' Is this expected behavior? Anything that can be done about it? Environment: ============ stunnel 5.80 on x86_64-redhat-linux-gnu platform Compiled/running with OpenSSL 3.5.7 9 Jun 2026 Threading:PTHREAD Sockets:POLL,IPv6,SYSTEMD TLS:ENGINE,FIPS,OCSP,PSK,SNI,DTLS Global options: fips = no RNDbytes = 1024 RNDfile = /dev/urandom RNDoverwrite = yes Service-level options: ciphers = PROFILE=SYSTEM (with "fips = yes") ciphers = PROFILE=SYSTEM (with "fips = no") ciphersuites = TLS_AES_256_GCM_SHA384:TLS_AES_128_GCM_SHA256:TLS_CHACHA20_POLY1305_SHA256 (with TLSv1.3) curves = P-256:P-521:P-384 (with "fips = yes") curves = X25519MLKEM768:X25519:P-256:X448:P-521:P-384 (with "fips = no") debug = daemon.notice logId = sequential options = NO_SSLv2 options = NO_SSLv3 securityLevel = 2 sessionCacheSize = 1000 sessionCacheTimeout = 300 seconds stack = 131072 bytes TIMEOUTbusy = 300 seconds TIMEOUTclose = 60 seconds TIMEOUTconnect = 10 seconds TIMEOUTidle = 43200 seconds TIMEOUTocsp = 5 seconds verify = none stunnel.conf: ============= debug = warning [switch2-frontend] accept = 0.0.0.0:8402 CAfile = /etc/ipa/ca.crt cert = /etc/pki/tls/certs/stunnel/switch2.crt key = /tmp/keys/switch2.key connect = 127.255.255.254:8082 [switch2-backend] client = yes accept = 127.255.255.254:8082 connect = 172.31.4.2:443 verifyChain = yes checkHost = switch2.penurio.us CAfile = /etc/pki/tls/certs/stunnel/switch-ca.crt sslVersion = TLSv1 ciphers = DHE-RSA-AES256-SHA options = ALLOW_UNSAFE_LEGACY_RENEGOTIATION securityLevel = 0 OCSPrequire = no OCSPaia = no [switch4-frontend] accept = 0.0.0.0:8404 CAfile = /etc/ipa/ca.crt cert = /etc/pki/tls/certs/stunnel/switch4.crt key = /tmp/keys/switch4.key connect = 127.255.255.254:8084 [switch4-backend] client = yes accept = 127.255.255.254:8084 connect = 172.31.4.7:443 verifyChain = yes checkHost = switch4.penurio.us CAfile = /etc/pki/tls/certs/stunnel/switch-ca.crt sslVersion = TLSv1 ciphers = DHE-RSA-AES256-SHA options = ALLOW_UNSAFE_LEGACY_RENEGOTIATION securityLevel = 0 OCSPrequire = no OCSPaia = no -- ======================================================================== If your user interface is intuitive in retrospect ... it isn't intuitive ========================================================================