This is a note to let you know that I've just added the patch titled
rt2800usb: slow down TX status polling
to the 3.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
rt2800usb-slow-down-tx-status-polling.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 36165fd5b00bf8163f89c21bb16a3e9834555b10 Mon Sep 17 00:00:00 2001
From: Stanislaw Gruszka <sgruszka@xxxxxxxxxx>
Date: Fri, 18 Oct 2013 11:36:54 +0200
Subject: rt2800usb: slow down TX status polling
From: Stanislaw Gruszka <sgruszka@xxxxxxxxxx>
commit 36165fd5b00bf8163f89c21bb16a3e9834555b10 upstream.
Polling TX statuses too frequently has two negative effects. First is
randomly peek CPU usage, causing overall system functioning delays.
Second bad effect is that device is not able to fill TX statuses in
H/W register on some workloads and we get lot of timeouts like below:
ieee80211 phy4: rt2800usb_entry_txstatus_timeout: Warning - TX status timeout for entry 7 in queue 2
ieee80211 phy4: rt2800usb_entry_txstatus_timeout: Warning - TX status timeout for entry 7 in queue 2
ieee80211 phy4: rt2800usb_txdone: Warning - Got TX status for an empty queue 2, dropping
This not only cause flood of messages in dmesg, but also bad throughput,
since rate scaling algorithm can not work optimally.
In the future, we should probably make polling interval be adjusted
automatically, but for now just increase values, this make mentioned
problems gone.
Resolve:
https://bugzilla.kernel.org/show_bug.cgi?id=62781
Signed-off-by: Stanislaw Gruszka <sgruszka@xxxxxxxxxx>
Signed-off-by: John W. Linville <linville@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/net/wireless/rt2x00/rt2800usb.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
--- a/drivers/net/wireless/rt2x00/rt2800usb.c
+++ b/drivers/net/wireless/rt2x00/rt2800usb.c
@@ -143,6 +143,8 @@ static bool rt2800usb_txstatus_timeout(s
return false;
}
+#define TXSTATUS_READ_INTERVAL 1000000
+
static bool rt2800usb_tx_sta_fifo_read_completed(struct rt2x00_dev *rt2x00dev,
int urb_status, u32 tx_status)
{
@@ -170,8 +172,9 @@ static bool rt2800usb_tx_sta_fifo_read_c
queue_work(rt2x00dev->workqueue, &rt2x00dev->txdone_work);
if (rt2800usb_txstatus_pending(rt2x00dev)) {
- /* Read register after 250 us */
- hrtimer_start(&rt2x00dev->txstatus_timer, ktime_set(0, 250000),
+ /* Read register after 1 ms */
+ hrtimer_start(&rt2x00dev->txstatus_timer,
+ ktime_set(0, TXSTATUS_READ_INTERVAL),
HRTIMER_MODE_REL);
return false;
}
@@ -196,8 +199,9 @@ static void rt2800usb_async_read_tx_stat
if (test_and_set_bit(TX_STATUS_READING, &rt2x00dev->flags))
return;
- /* Read TX_STA_FIFO register after 500 us */
- hrtimer_start(&rt2x00dev->txstatus_timer, ktime_set(0, 500000),
+ /* Read TX_STA_FIFO register after 2 ms */
+ hrtimer_start(&rt2x00dev->txstatus_timer,
+ ktime_set(0, 2*TXSTATUS_READ_INTERVAL),
HRTIMER_MODE_REL);
}
Patches currently in stable-queue which might be from sgruszka@xxxxxxxxxx are
queue-3.4/rt2800usb-slow-down-tx-status-polling.patch
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