4 ms·

Is there a reason why you’re not using libdispatch on darwin and instead using kqueue directly?

jorangreef 4y ago
At the time, we wanted to get macOS or Darwin running as soon as possible to improve the local developer experience, but—we've always had a soft spot for FreeBSD so kqueue was two birds in one!
kprotty 4y ago
King from TigerBeetle here. One of the reasons is that libdispatch's I/O functions introduce extra dynamic allocations for internal queueing via `dispatch_async` ([0],[1],[2]) and from an API perspective of realloc-ing [3] an internally owned [4] buffer. TigerBeetle, on the other hand, statically allocates all I/O buffers upfront [5], treats these buffers as intrusively-provided typed data [6] (no growing/owned buffers), and does internal queueing without synchronization or dynamic allocation [7]. [0]: https://github.com/apple/swift-corelibs-libdispatch/blob/469c8ecfa0011f5da23acacf8658b6a60a899a78/src/queue.c#L889 https://github.com/apple/swift-corelibs-libdispatch/blob/469... [1]: https://github.com/apple/swift-corelibs-libdispatch/blob/469c8ecfa0011f5da23acacf8658b6a60a899a78/src/io.c#L847-L860 https://github.com/apple/swift-corelibs-libdispatch/blob/469... [2]: https://github.com/apple/swift-corelibs-libdispatch/blob/469c8ecfa0011f5da23acacf8658b6a60a899a78/src/io.c#L1178-L1190 https://github.com/apple/swift-corelibs-libdispatch/blob/469... [3]: https://github.com/apple/swift-corelibs-libdispatch/blob/469c8ecfa0011f5da23acacf8658b6a60a899a78/src/io.c#L2325-L2361 https://github.com/apple/swift-corelibs-libdispatch/blob/469... [4]: https://developer.apple.com/documentation/dispatch/1388933-dispatch_read https://developer.apple.com/documentation/dispatch/1388933-d... [5]: https://tigerbeetle.com/blog/a-database-without-dynamic-memory/ https://tigerbeetle.com/blog/a-database-without-dynamic-memo... [6]: https://github.com/tigerbeetledb/tigerbeetle/blob/d15acc663f8882cb02413129e8351bf3238335e6/src/message_bus.zig#L676-L685 https://github.com/tigerbeetledb/tigerbeetle/blob/d15acc663f... [7]: https://github.com/tigerbeetledb/tigerbeetle/d15acc663f8882cb02413129e8351bf3238335e6/main/src/io/darwin.zig#L16-L18 https://github.com/tigerbeetledb/tigerbeetle/d15acc663f8882c...
- williamcotton 4y ago
  Thank you! I was indeed looking for the technical details!

At the time, we wanted to get macOS or Darwin running as soon as possible to improve the local developer experience, but—we've always had a soft spot for FreeBSD so kqueue was two birds in one!

kprotty 4y ago

King from TigerBeetle here. One of the reasons is that libdispatch's I/O functions introduce extra dynamic allocations for internal queueing via `dispatch_async` ([0],[1],[2]) and from an API perspective of realloc-ing [3] an internally owned [4] buffer. TigerBeetle, on the other hand, statically allocates all I/O buffers upfront [5], treats these buffers as intrusively-provided typed data [6] (no growing/owned buffers), and does internal queueing without synchronization or dynamic allocation [7]. [0]: https://github.com/apple/swift-corelibs-libdispatch/blob/469c8ecfa0011f5da23acacf8658b6a60a899a78/src/queue.c#L889 https://github.com/apple/swift-corelibs-libdispatch/blob/469... [1]: https://github.com/apple/swift-corelibs-libdispatch/blob/469c8ecfa0011f5da23acacf8658b6a60a899a78/src/io.c#L847-L860 https://github.com/apple/swift-corelibs-libdispatch/blob/469... [2]: https://github.com/apple/swift-corelibs-libdispatch/blob/469c8ecfa0011f5da23acacf8658b6a60a899a78/src/io.c#L1178-L1190 https://github.com/apple/swift-corelibs-libdispatch/blob/469... [3]: https://github.com/apple/swift-corelibs-libdispatch/blob/469c8ecfa0011f5da23acacf8658b6a60a899a78/src/io.c#L2325-L2361 https://github.com/apple/swift-corelibs-libdispatch/blob/469... [4]: https://developer.apple.com/documentation/dispatch/1388933-dispatch_read https://developer.apple.com/documentation/dispatch/1388933-d... [5]: https://tigerbeetle.com/blog/a-database-without-dynamic-memory/ https://tigerbeetle.com/blog/a-database-without-dynamic-memo... [6]: https://github.com/tigerbeetledb/tigerbeetle/blob/d15acc663f8882cb02413129e8351bf3238335e6/src/message_bus.zig#L676-L685 https://github.com/tigerbeetledb/tigerbeetle/blob/d15acc663f... [7]: https://github.com/tigerbeetledb/tigerbeetle/d15acc663f8882cb02413129e8351bf3238335e6/main/src/io/darwin.zig#L16-L18 https://github.com/tigerbeetledb/tigerbeetle/d15acc663f8882c...

williamcotton 4y ago
Thank you! I was indeed looking for the technical details!