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bobbee · Posted: Mon Nov 10, 2025 11:29 am Post subject: swappiness and network settings

Customer is asking if there are suggested setting for MQ. I have never seen these.

Swappiness
? REL 8 default is 60
? REL 8 also really started pushing cgroups, so it?s no longer enough to just set swappiness
? RedHat recommends 60 because SSD?s have become blazingly fast
? SSD speed isn?t our issue though, any data written to disk is synchronously replicated which kills us for SWAP.

Net mem
? Using the default net memory settings means that max and default are the same
? This severely limits TCP window scaling (typically to 65k max)
? Increasing the max allows the window to grow as needed to fit the data flow
? Small windows limit how much data can be received before the sender needs to stop and wait for the other side to catch up.

Server = samp09dc
mem = 64G
vm.swappiness = 60
net.core.rmem_default = 212992
net.core.rmem_max = 212992
net.core.wmem_default = 212992
net.core.wmem_max = 212992
net.ipv4.tcp_mem = 1588242 2117659 3176484
net.ipv4.tcp_rmem = 4096 87380 6291456
net.ipv4.tcp_wmem = 4096 16384 4194304