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authorGravatar Mikkel Kamstrup Erlandsen2014-03-20 10:01:53 +0100
committerGravatar Martin Szulecki2014-03-24 17:01:30 +0100
commit8ba560fdd177f107c5a0cf667d4e4ab3b0c59f4a (patch)
tree1d9a1707cab915103074849cc6f5fb8b234f5c20 /src
parentd06ea10f14a806f2770507cd179b62c0d4eda6a2 (diff)
downloadusbmuxd-8ba560fdd177f107c5a0cf667d4e4ab3b0c59f4a.tar.gz
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usb-linux: massive read perf improvement with 3 parallel transfers
By maintaining 3 parallel usb trasfers when reading we get 2-3x more throughput when reading. Without this the usb port is mostly just idling. I get 23mb/s on my system compared to a clean Apple stack that gives me 17mb/s. 3 was chosen because it is simple to hard code, gives very good performance, and have very little impact on out resource consumption.
Diffstat (limited to 'src')
-rw-r--r--src/usb-linux.c107
1 files changed, 73 insertions, 34 deletions
diff --git a/src/usb-linux.c b/src/usb-linux.c
index 94db8f2..40bf502 100644
--- a/src/usb-linux.c
+++ b/src/usb-linux.c
@@ -4,6 +4,7 @@
Copyright (C) 2009 Hector Martin "marcan" <hector@marcansoft.com>
Copyright (C) 2009 Nikias Bassen <nikias@gmx.li>
Copyright (C) 2009 Martin Szulecki <opensuse@sukimashita.com>
+Copyright (C) 2014 Mikkel Kamstrup Erlandsen <mikkel.kamstrup@xamarin.com>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
@@ -39,6 +40,12 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
// we need this because there is currently no asynchronous device discovery mechanism in libusb
#define DEVICE_POLL_TIME 1000
+// Number of parallel bulk transfers we have running for reading data from the device.
+// Older versions of usbmuxd kept only 1, which leads to a mostly dormant USB port.
+// 3 seems to be an all round sensible number - giving better read perf than
+// Apples usbmuxd, at least.
+#define NUM_RX_LOOPS 3
+
struct usb_device {
libusb_device_handle *dev;
uint8_t bus, address;
@@ -46,7 +53,7 @@ struct usb_device {
char serial[256];
int alive;
uint8_t interface, ep_in, ep_out;
- struct libusb_transfer *rx_xfer;
+ struct collection rx_xfers;
struct collection tx_xfers;
int wMaxPacketSize;
};
@@ -64,17 +71,20 @@ static void usb_disconnect(struct usb_device *dev)
return;
}
- // kill the rx xfer and tx xfers and try to make sure the callbacks get called before we free the device
- if(dev->rx_xfer) {
- usbmuxd_log(LL_DEBUG, "usb_disconnect: cancelling RX xfer");
- libusb_cancel_transfer(dev->rx_xfer);
- }
+ // kill the rx xfer and tx xfers and try to make sure the callbacks
+ // get called before we free the device
+ FOREACH(struct libusb_transfer *xfer, &dev->rx_xfers) {
+ usbmuxd_log(LL_DEBUG, "usb_disconnect: cancelling RX xfer %p", xfer);
+ libusb_cancel_transfer(xfer);
+ } ENDFOREACH
+
FOREACH(struct libusb_transfer *xfer, &dev->tx_xfers) {
usbmuxd_log(LL_DEBUG, "usb_disconnect: cancelling TX xfer %p", xfer);
libusb_cancel_transfer(xfer);
} ENDFOREACH
- while(dev->rx_xfer || collection_count(&dev->tx_xfers)) {
+ // Busy-wait until all xfers are closed
+ while(collection_count(&dev->rx_xfers) || collection_count(&dev->tx_xfers)) {
struct timeval tv;
int res;
@@ -85,7 +95,9 @@ static void usb_disconnect(struct usb_device *dev)
break;
}
}
+
collection_free(&dev->tx_xfers);
+ collection_free(&dev->rx_xfers);
libusb_release_interface(dev->dev, dev->interface);
libusb_close(dev->dev);
dev->dev = NULL;
@@ -93,6 +105,15 @@ static void usb_disconnect(struct usb_device *dev)
free(dev);
}
+static void reap_dead_devices(void) {
+ FOREACH(struct usb_device *usbdev, &device_list) {
+ if(!usbdev->alive) {
+ device_remove(usbdev);
+ usb_disconnect(usbdev);
+ }
+ } ENDFOREACH
+}
+
// Callback from write operation
static void tx_callback(struct libusb_transfer *xfer)
{
@@ -201,9 +222,11 @@ static void rx_callback(struct libusb_transfer *xfer)
// this should never be reached.
break;
}
+
free(xfer->buffer);
- dev->rx_xfer = NULL;
+ collection_remove(&dev->rx_xfers, xfer);
libusb_free_transfer(xfer);
+
// we can't usb_disconnect here due to a deadlock, so instead mark it as dead and reap it after processing events
// we'll do device_remove there too
dev->alive = 0;
@@ -211,19 +234,21 @@ static void rx_callback(struct libusb_transfer *xfer)
}
// Start a read-callback loop for this device
-static int start_rx(struct usb_device *dev)
+static int start_rx_loop(struct usb_device *dev)
{
int res;
void *buf;
- dev->rx_xfer = libusb_alloc_transfer(0);
+ struct libusb_transfer *xfer = libusb_alloc_transfer(0);
buf = malloc(USB_MRU);
- libusb_fill_bulk_transfer(dev->rx_xfer, dev->dev, dev->ep_in, buf, USB_MRU, rx_callback, dev, 0);
- if((res = libusb_submit_transfer(dev->rx_xfer)) != 0) {
+ libusb_fill_bulk_transfer(xfer, dev->dev, dev->ep_in, buf, USB_MRU, rx_callback, dev, 0);
+ if((res = libusb_submit_transfer(xfer)) != 0) {
usbmuxd_log(LL_ERROR, "Failed to submit RX transfer to device %d-%d: %d", dev->bus, dev->address, res);
- libusb_free_transfer(dev->rx_xfer);
- dev->rx_xfer = NULL;
+ libusb_free_transfer(xfer);
return res;
}
+
+ collection_add(&dev->rx_xfers, xfer);
+
return 0;
}
@@ -253,10 +278,14 @@ int usb_discover(void)
usbmuxd_log(LL_SPEW, "usb_discover: scanning %d devices", cnt);
+ // Mark all devices as dead, and do a mark-sweep like
+ // collection of dead devices
FOREACH(struct usb_device *usbdev, &device_list) {
usbdev->alive = 0;
} ENDFOREACH
+ // Enumerate all USB devices and mark the ones we already know
+ // about as live, again
for(i=0; i<cnt; i++) {
// the following are non-blocking operations on the device list
libusb_device *dev = devs[i];
@@ -407,6 +436,7 @@ int usb_discover(void)
}
collection_init(&usbdev->tx_xfers);
+ collection_init(&usbdev->rx_xfers);
collection_add(&device_list, usbdev);
@@ -414,19 +444,37 @@ int usb_discover(void)
usb_disconnect(usbdev);
continue;
}
- if(start_rx(usbdev) < 0) {
+
+ // Spin up NUM_RX_LOOPS parallel usb data retrieval loops
+ // Old usbmuxds used only 1 rx loop, but that leaves the
+ // USB port sleeping most of the time
+ int rx_loops = NUM_RX_LOOPS;
+ for (rx_loops = NUM_RX_LOOPS; rx_loops > 0; rx_loops--) {
+ if(start_rx_loop(usbdev) < 0) {
+ usbmuxd_log(LL_WARNING, "Failed to start RX loop number %d", NUM_RX_LOOPS - rx_loops);
+ }
+ }
+
+ // Ensure we have at least 1 RX loop going
+ if (rx_loops == NUM_RX_LOOPS) {
+ usbmuxd_log(LL_FATAL, "Failed to start any RX loop for device %d-%d",
+ usbdev->bus, usbdev->address);
device_remove(usbdev);
usb_disconnect(usbdev);
continue;
+ } else if (rx_loops > 0) {
+ usbmuxd_log(LL_WARNING, "Failed to start all %d RX loops. Going on with %d loops. "
+ "This may have negative impact on device read speed.",
+ NUM_RX_LOOPS, NUM_RX_LOOPS - rx_loops);
+ } else {
+ usbmuxd_log(LL_DEBUG, "All %d RX loops started successfully", NUM_RX_LOOPS);
}
+
valid_count++;
}
- FOREACH(struct usb_device *usbdev, &device_list) {
- if(!usbdev->alive) {
- device_remove(usbdev);
- usb_disconnect(usbdev);
- }
- } ENDFOREACH
+
+ // Clean out any device we didn't mark back as live
+ reap_dead_devices();
libusb_free_device_list(devs, 1);
@@ -530,13 +578,9 @@ int usb_process(void)
usbmuxd_log(LL_ERROR, "libusb_handle_events_timeout failed: %d", res);
return res;
}
+
// reap devices marked dead due to an RX error
- FOREACH(struct usb_device *usbdev, &device_list) {
- if(!usbdev->alive) {
- device_remove(usbdev);
- usb_disconnect(usbdev);
- }
- } ENDFOREACH
+ reap_dead_devices();
if(dev_poll_remain_ms() <= 0) {
res = usb_discover();
@@ -570,13 +614,8 @@ int usb_process_timeout(int msec)
return res;
}
// reap devices marked dead due to an RX error
- FOREACH(struct usb_device *usbdev, &device_list) {
- if(!usbdev->alive) {
- device_remove(usbdev);
- usb_disconnect(usbdev);
- }
- } ENDFOREACH
- gettimeofday(&tcur, NULL);
+ reap_dead_devices();
+ gettimeofday(&tcur, NULL);
}
return 0;
}