macos get_interfaces is extremly slow with larger amount of interfaces (sometimes) #143

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1. shellrow commented on Dec 13, 2025

   

   shellrow

   on Dec 13, 2025

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   Thanks for the report and the investigation!

   One clarification from the current codebase: on macOS, interfaces() already uses getifaddrs via unix_interfaces() to enumerate interfaces. However, we also call get_if_type_map() to enrich the data (interface type and display name), and get_if_type_map() internally uses system_configuration::network_configuration::get_interfaces().

   So even though the base interface listing itself is fast, the SystemConfiguration lookup still runs each time and may block depending on the environment (for example, configd state, VPNs, or Network Extensions).

   I also measured a detailed breakdown on my machines (24 interfaces present), which makes the bottleneck very clear:

   • Time taken to build SCInterface map (SystemConfiguration): ~13.7 ms
   • Time taken to enumerate unix interfaces via getifaddrs: ~0.8 ms
   • Total time for interfaces() (24 interfaces): ~15.5 ms

   So the vast majority of the time is spent inside the SystemConfiguration-based lookup. And it’s clear that if network_configuration::get_interfaces() blocks, the total call time will scale accordingly.

   We’ll next look into how to avoid this slow path by default while keeping interface type/name information available when possible.
2. dignifiedquire commented on Dec 13, 2025

   

   dignifiedquire

   on Dec 13, 2025

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   Thanks for the quick reply. Following up I did some measurements on my machine, and can confirm your numbers

   network_configuration::get_interfaces: 1758ms
   get_if_type_map: 1948ms
   unix_interfaces: 0ms
   gateway_map: 0ms
   assign gateway: 0ms
   default iface/dns_servers: 0ms
   got interfaces 21 after 1.9491s
   

   (funny enough, today it got a bit faster again)
3. shellrow

   linked a pull request that will close this issueperf(macos): speed up interface enumeration #144on Dec 14, 2025
4. shellrow commented on Dec 14, 2025

   

   shellrow

   on Dec 14, 2025

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   Thanks for running the measurements!

   I've implemented a performance improvement on the perf(macos): speed up interface enumeration #144 .

   Benchmark results on my machine (22 interfaces):
   Before (release):

   • Total: ~13–15 ms

   After (release):

   • Total: ~1.9–2.0 ms

   This is 7x speed improvement, with the interface-type and friendly-name resolution itself becoming ~40x faster.

   Thanks again!
5. shellrow

   closed this as completedin #144on Dec 15, 2025