From 8a2bcebd60cfad977ad8ff419a9878915d77df7b Mon Sep 17 00:00:00 2001
From: Robby Zambito <contact@robbyzambito.me>
Date: Sat, 10 Jan 2026 16:54:25 -0500
Subject: Cache align hot buffers

---
 src/Server.zig | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

(limited to 'src/Server.zig')

diff --git a/src/Server.zig b/src/Server.zig
index ad07564..cc16408 100644
--- a/src/Server.zig
+++ b/src/Server.zig
@@ -164,19 +164,19 @@ fn handleConnection(
         server_allocator;
 
     // Set up client writer
-    const w_buffer: []u8 = try alloc.alloc(u8, w_buf_size);
+    const w_buffer: []u8 = try alloc.alignedAlloc(u8, .@"64", w_buf_size);
     defer alloc.free(w_buffer);
     var writer = stream.writer(io, w_buffer);
     const out = &writer.interface;
 
     // Set up client reader
-    const r_buffer: []u8 = try alloc.alloc(u8, r_buf_size);
+    const r_buffer: []u8 = try alloc.alignedAlloc(u8, .@"64", r_buf_size);
     defer alloc.free(r_buffer);
     var reader = stream.reader(io, r_buffer);
     const in = &reader.interface;
 
     // Set up buffer queue
-    const qbuf: []u8 = try alloc.alloc(u8, r_buf_size);
+    const qbuf: []u8 = try alloc.alignedAlloc(u8, .@"64", 256 * 1024 * 1024);
     defer alloc.free(qbuf);
     var recv_queue: Queue(u8) = .init(qbuf);
     defer recv_queue.close(io);
@@ -443,14 +443,18 @@ fn unsubscribe(
     }
 }
 
+// TODO: The probed system value is too low.
+// Setting the value higher leads to higher throughput.
+// Find a more appropriate value.
+// It should be the probed value at a minimum.
 /// Probes the system for an appropriate buffer size.
 /// Try to match the kernel socket buffers to maximize
 /// the amount of data we push through each syscall.
 fn getBufferSizes(io: Io) @Tuple(&.{ usize, usize }) {
-    const default_size = 128 * 1024 * 1024;
+    const default_size = 4 * 1024;
     const default = .{ default_size, default_size };
 
-    if (true) return default;
+    // if (true) return default;
 
     const dir = Dir.openDirAbsolute(io, "/proc/sys/net/core", .{}) catch {
         log.warn("couldn't open /proc/sys/net/core", .{});
@@ -459,8 +463,8 @@ fn getBufferSizes(io: Io) @Tuple(&.{ usize, usize }) {
 
     var buf: [64]u8 = undefined;
 
-    const rmem_max = readBufferSize(io, dir, "rmem_max", &buf, default_size);
-    const wmem_max = readBufferSize(io, dir, "wmem_max", &buf, default_size);
+    const rmem_max = readBufferSize(io, dir, "rmem_max", &buf, default_size) * 2;
+    const wmem_max = readBufferSize(io, dir, "wmem_max", &buf, default_size) * 2;
 
     return .{ rmem_max, wmem_max };
 }
-- 
cgit