From 077e41b0a9a4924f3a302cbd6f09b090ccd7304e Mon Sep 17 00:00:00 2001
From: Saza-ku <the.latticeheart@gmail.com>
Date: Mon, 5 Feb 2024 00:54:41 +0900
Subject: [PATCH] virtio net: interrupt coalescing when sending packets

---
 src/drivers/virtio/common.zig |  4 ++++
 src/drivers/virtio/net.zig    | 22 +++++++++++++---------
 src/timer.zig                 |  3 +++
 3 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/src/drivers/virtio/common.zig b/src/drivers/virtio/common.zig
index 16e8d5fd..4d9520dd 100644
--- a/src/drivers/virtio/common.zig
+++ b/src/drivers/virtio/common.zig
@@ -530,6 +530,10 @@ pub fn VirtioMmioTransport(comptime DeviceConfigType: type) type {
         }
 
         pub fn notifyQueue(self: *Self, virtq: *Virtqueue) void {
+            if (virtq.not_notified_num_descs == 0) {
+                return;
+            }
+
             self.common_config.queue_select = virtq.index;
             @fence(std.builtin.AtomicOrder.SeqCst);
             const offset = self.notify_off_multiplier * self.common_config.queue_notify_off;
diff --git a/src/drivers/virtio/net.zig b/src/drivers/virtio/net.zig
index 8e611ea9..255c2e90 100644
--- a/src/drivers/virtio/net.zig
+++ b/src/drivers/virtio/net.zig
@@ -129,17 +129,17 @@ const VirtioNet = struct {
         const buf = @as([*]u8, @ptrFromInt(base + @sizeOf(Header)));
         @memcpy(buf, data);
 
-        var desc_buf = [_]common.VirtqDescBuffer{ common.VirtqDescBuffer{
+        var desc_buf = [_]common.VirtqDescBuffer{common.VirtqDescBuffer{
             .addr = base,
-            .len = @sizeOf(Header),
+            .len = @sizeOf(Header) + @as(u32, @intCast(data.len)),
             .type = common.VirtqDescBufferType.ReadonlyFromDevice,
-        }, common.VirtqDescBuffer{
-            .addr = base + @sizeOf(Header),
-            .len = @as(u32, @intCast(data.len)),
-            .type = common.VirtqDescBufferType.ReadonlyFromDevice,
-        } };
-        self.transmitq().enqueue(desc_buf[0..2]);
-        self.virtio.transport.notifyQueue(self.transmitq());
+        }};
+
+        self.transmitq().enqueue(desc_buf[0..1]);
+
+        if (self.transmitq().not_notified_num_descs > self.transmitq().num_descs / 2) {
+            self.virtio.transport.notifyQueue(self.transmitq());
+        }
     }
 
     pub fn receive(self: *Self) void {
@@ -207,3 +207,7 @@ fn handleIrq(frame: *interrupt.InterruptFrame) void {
     log.debug.print("interrupt\n");
     virtio_net.receive();
 }
+
+pub fn flush() void {
+    virtio_net.virtio.transport.notifyQueue(virtio_net.transmitq());
+}
diff --git a/src/timer.zig b/src/timer.zig
index 31a45d2c..324305b5 100644
--- a/src/timer.zig
+++ b/src/timer.zig
@@ -2,6 +2,7 @@ const std = @import("std");
 const heap = @import("heap.zig");
 const interrupt = @import("interrupt.zig");
 const sync = @import("sync.zig");
+const net = @import("drivers/virtio/net.zig");
 
 const Allocator = std.mem.Allocator;
 const ArrayList = std.ArrayList;
@@ -58,6 +59,8 @@ pub fn handleIrq(frame: *interrupt.InterruptFrame) void {
         }
     }
     timers.release();
+
+    net.flush();
 }
 
 pub fn init() void {