high CPU usage in FlyingSocks

[lhoward]

Still investigating this, potentially I am ’holding it wrong’. We are seeing this on Linux in OpenSRP, which uses FlyingFox to host a REST server for monitoring. perf data is below, I'm retesting with debug symbols now, just need to wait for the issue to recur.

cc @nippoo @ideoforms

[lhoward]

Note, the server is not under load / handling any requests.

[lhoward]

Also, note perf output can be confusing, it's a percentage of total runtime (so 100% doesn't mean the CPU is 100% loaded), but we were seeing 25% CPU usage (which on a 4 core CM4 suggests a CPU core was pinned).

[lhoward]

This might be a little easier to parse.

[lhoward]

FWIW Claude thinks this is the fix:

diff --git a/FlyingSocks/Sources/SocketPool+ePoll.swift b/FlyingSocks/Sources/SocketPool+ePoll.swift
index a104e01..9a6f3b4 100644
--- a/FlyingSocks/Sources/SocketPool+ePoll.swift
+++ b/FlyingSocks/Sources/SocketPool+ePoll.swift
@@ -242,7 +242,9 @@ private struct EPOLLEvents: OptionSet, Hashable {
 private extension Socket.Events {
 
     var epollEvents: EPOLLEvents {
-        reduce(EPOLLEvents()) { [$0, $1.epollEvent] }
+        var events = reduce(EPOLLEvents()) { [$0, $1.epollEvent] }
+        events.insert(.edgeTriggered)
+        return events
     }

but this doesn't appear to fix the issue.