[SR-Users] Huge TLS performance regression migrating from 3.3.7 to 4.2.6

Hi List, I've been reaching a strange thing lately, trying to upgrade to kamailio 4.2.6 ( identical config ): - 35% loss of performance on TLS connections ( Sipp REGISTER scenario, easily reproduced ). - more TCP workers needed to ease the TCP queues ( 32 workers on 3.3.7, at least 64 are needed on 4.2.6 to avoid "queue full" messages in logs ). - kamailio 4.2.6 intermittent processing of requests ( Kamailio stops accepting new tcp connections, then resume a bit later, then stops again,... ) => starts happening when Kamailio is treating more than 20k tcp connections, with between 500-1k req/s. During those periods, trying to connect to kamailio with an openssl s_client -connect will end up in a timeout or with a long delay before the certificate is received ( 03 CONNECTED ). - kamailio 4.2.6 dropping connections, kamailio 3.3.7 keeping those connections: after a while, the number of active connections starts to decrease on kam4, on kam3 it stays constant. I was wondering if I was alone in this situation or if someone else is impacted, has some advices ? It does not seem to be a config issue, as it is the same that was deployed with both versions.