This implements a very naive dynamic queue limits
on the flat HTT Tx. In some of my tests (using
flent) it seems to reduce induced latency by
orders of magnitude (e.g. when enforcing 6mbps
tx rates 2500ms -> 150ms). But at the same time it
introduces TCP throughput buildup over time
(instead of immediate bump to max). More
importantly I didn't observe it to make things
much worse (yet).
Signed-off-by: Michal Kazior <[email protected]>
---
I'm not sure yet if it's worth to consider this
patch for merging per se. My motivation was to
have something to prove mac80211 fq works and to
see if DQL can learn the proper queue limit in
face of wireless rate control at all.
I'll do a follow up post with flent test results
and some notes.
drivers/net/wireless/ath/ath10k/core.h | 2 ++
drivers/net/wireless/ath/ath10k/htt_rx.c | 12 ++++++++----
drivers/net/wireless/ath/ath10k/htt_tx.c | 8 +++++++-
drivers/net/wireless/ath/ath10k/mac.c | 26 ++++++++++++++++++++------
drivers/net/wireless/ath/ath10k/txrx.c | 6 +++++-
drivers/net/wireless/ath/ath10k/txrx.h | 3 ++-
6 files changed, 44 insertions(+), 13 deletions(-)
diff --git a/drivers/net/wireless/ath/ath10k/core.h b/drivers/net/wireless/ath/ath10k/core.h
index b6c157ef705a..d8eebcd2b0b0 100644
--- a/drivers/net/wireless/ath/ath10k/core.h
+++ b/drivers/net/wireless/ath/ath10k/core.h
@@ -630,6 +630,8 @@ struct ath10k {
struct device *dev;
u8 mac_addr[ETH_ALEN];
+ struct dql dql;
+
enum ath10k_hw_rev hw_rev;
u16 dev_id;
u32 chip_id;
diff --git a/drivers/net/wireless/ath/ath10k/htt_rx.c b/drivers/net/wireless/ath/ath10k/htt_rx.c
index 2da8ccf3da05..38bc8bf46b67 100644
--- a/drivers/net/wireless/ath/ath10k/htt_rx.c
+++ b/drivers/net/wireless/ath/ath10k/htt_rx.c
@@ -1679,7 +1679,8 @@ static void ath10k_htt_rx_frag_handler(struct ath10k_htt *htt,
}
static void ath10k_htt_rx_frm_tx_compl(struct ath10k *ar,
- struct sk_buff *skb)
+ struct sk_buff *skb,
+ unsigned int *completed)
{
struct ath10k_htt *htt = &ar->htt;
struct htt_resp *resp = (struct htt_resp *)skb->data;
@@ -1712,7 +1713,7 @@ static void ath10k_htt_rx_frm_tx_compl(struct ath10k *ar,
for (i = 0; i < resp->data_tx_completion.num_msdus; i++) {
msdu_id = resp->data_tx_completion.msdus[i];
tx_done.msdu_id = __le16_to_cpu(msdu_id);
- ath10k_txrx_tx_unref(htt, &tx_done);
+ ath10k_txrx_tx_unref(htt, &tx_done, completed);
}
}
@@ -2354,7 +2355,7 @@ void ath10k_htt_t2h_msg_handler(struct ath10k *ar, struct sk_buff *skb)
break;
}
- status = ath10k_txrx_tx_unref(htt, &tx_done);
+ status = ath10k_txrx_tx_unref(htt, &tx_done, NULL);
if (!status) {
spin_lock_bh(&htt->tx_lock);
ath10k_htt_tx_mgmt_dec_pending(htt);
@@ -2482,6 +2483,7 @@ static void ath10k_htt_txrx_compl_task(unsigned long ptr)
struct htt_resp *resp;
struct sk_buff *skb;
unsigned long flags;
+ unsigned int completed = 0;
__skb_queue_head_init(&tx_q);
__skb_queue_head_init(&rx_q);
@@ -2505,10 +2507,12 @@ static void ath10k_htt_txrx_compl_task(unsigned long ptr)
spin_unlock_irqrestore(&htt->tx_fetch_ind_q.lock, flags);
while ((skb = __skb_dequeue(&tx_q))) {
- ath10k_htt_rx_frm_tx_compl(htt->ar, skb);
+ ath10k_htt_rx_frm_tx_compl(htt->ar, skb, &completed);
dev_kfree_skb_any(skb);
}
+ dql_completed(&htt->ar->dql, completed);
+
while ((skb = __skb_dequeue(&tx_ind_q))) {
ath10k_htt_rx_tx_fetch_ind(ar, skb);
dev_kfree_skb_any(skb);
diff --git a/drivers/net/wireless/ath/ath10k/htt_tx.c b/drivers/net/wireless/ath/ath10k/htt_tx.c
index b2ae122381ca..2b7f7802f9f1 100644
--- a/drivers/net/wireless/ath/ath10k/htt_tx.c
+++ b/drivers/net/wireless/ath/ath10k/htt_tx.c
@@ -367,7 +367,7 @@ static int ath10k_htt_tx_clean_up_pending(int msdu_id, void *skb, void *ctx)
tx_done.discard = 1;
tx_done.msdu_id = msdu_id;
- ath10k_txrx_tx_unref(htt, &tx_done);
+ ath10k_txrx_tx_unref(htt, &tx_done, NULL);
return 0;
}
@@ -378,6 +378,7 @@ void ath10k_htt_tx_free(struct ath10k_htt *htt)
idr_for_each(&htt->pending_tx, ath10k_htt_tx_clean_up_pending, htt->ar);
idr_destroy(&htt->pending_tx);
+ dql_reset(&htt->ar->dql);
if (htt->txbuf.vaddr) {
size = htt->max_num_pending_tx *
@@ -839,6 +840,7 @@ int ath10k_htt_tx(struct ath10k_htt *htt, enum ath10k_hw_txrx_mode txmode,
u16 freq = 0;
u32 frags_paddr = 0;
u32 txbuf_paddr;
+ size_t skb_len;
struct htt_msdu_ext_desc *ext_desc = NULL;
spin_lock_bh(&htt->tx_lock);
@@ -1000,12 +1002,16 @@ int ath10k_htt_tx(struct ath10k_htt *htt, enum ath10k_hw_txrx_mode txmode,
sg_items[1].paddr = skb_cb->paddr;
sg_items[1].len = prefetch_len;
+ skb_len = msdu->len;
+
res = ath10k_hif_tx_sg(htt->ar,
htt->ar->htc.endpoint[htt->eid].ul_pipe_id,
sg_items, ARRAY_SIZE(sg_items));
if (res)
goto err_unmap_msdu;
+ dql_queued(&ar->dql, skb_len);
+
return 0;
err_unmap_msdu:
diff --git a/drivers/net/wireless/ath/ath10k/mac.c b/drivers/net/wireless/ath/ath10k/mac.c
index ed00853ea9cc..c848049ffdf3 100644
--- a/drivers/net/wireless/ath/ath10k/mac.c
+++ b/drivers/net/wireless/ath/ath10k/mac.c
@@ -3755,23 +3755,35 @@ void ath10k_mac_tx_push_pending(struct ath10k *ar)
struct ieee80211_hw *hw = ar->hw;
struct ieee80211_txq *txq;
struct ath10k_txq *artxq;
- struct ath10k_txq *last;
int ret;
int max;
spin_lock_bh(&ar->txqs_lock);
rcu_read_lock();
- last = list_last_entry(&ar->txqs, struct ath10k_txq, list);
- while (!list_empty(&ar->txqs)) {
+ for (;;) {
+ if (list_empty(&ar->txqs))
+ break;
+
+ if (dql_avail(&ar->dql) < 0)
+ break;
+
artxq = list_first_entry(&ar->txqs, struct ath10k_txq, list);
txq = container_of((void *)artxq, struct ieee80211_txq,
drv_priv);
- /* Prevent aggressive sta/tid taking over tx queue */
max = 16;
ret = 0;
- while (ath10k_mac_tx_can_push(hw, txq) && max--) {
+ for (;;) {
+ if (!max--)
+ break;
+
+ if (!ath10k_mac_tx_can_push(hw, txq))
+ break;
+
+ if (dql_avail(&ar->dql) < 0)
+ break;
+
ret = ath10k_mac_tx_push_txq(hw, txq);
if (ret < 0)
break;
@@ -3783,7 +3795,7 @@ void ath10k_mac_tx_push_pending(struct ath10k *ar)
ath10k_htt_tx_txq_update(hw, txq);
- if (artxq == last || (ret < 0 && ret != -ENOENT))
+ if (ret < 0 && ret != -ENOENT)
break;
}
@@ -4331,6 +4343,8 @@ static int ath10k_start(struct ieee80211_hw *hw)
mutex_lock(&ar->conf_mutex);
+ dql_init(&ar->dql, HZ);
+
switch (ar->state) {
case ATH10K_STATE_OFF:
ar->state = ATH10K_STATE_ON;
diff --git a/drivers/net/wireless/ath/ath10k/txrx.c b/drivers/net/wireless/ath/ath10k/txrx.c
index 48e26cdfe9a5..122c8edf10a1 100644
--- a/drivers/net/wireless/ath/ath10k/txrx.c
+++ b/drivers/net/wireless/ath/ath10k/txrx.c
@@ -50,7 +50,8 @@ out:
}
int ath10k_txrx_tx_unref(struct ath10k_htt *htt,
- const struct htt_tx_done *tx_done)
+ const struct htt_tx_done *tx_done,
+ unsigned int *completed)
{
struct ath10k *ar = htt->ar;
struct device *dev = ar->dev;
@@ -87,6 +88,9 @@ int ath10k_txrx_tx_unref(struct ath10k_htt *htt,
if (txq)
artxq->num_fw_queued--;
+ if (completed)
+ *completed += msdu->len;
+
ath10k_htt_tx_free_msdu_id(htt, tx_done->msdu_id);
ath10k_htt_tx_dec_pending(htt);
if (htt->num_pending_tx == 0)
diff --git a/drivers/net/wireless/ath/ath10k/txrx.h b/drivers/net/wireless/ath/ath10k/txrx.h
index e7ea1ae1c438..3a655270bcc5 100644
--- a/drivers/net/wireless/ath/ath10k/txrx.h
+++ b/drivers/net/wireless/ath/ath10k/txrx.h
@@ -20,7 +20,8 @@
#include "htt.h"
int ath10k_txrx_tx_unref(struct ath10k_htt *htt,
- const struct htt_tx_done *tx_done);
+ const struct htt_tx_done *tx_done,
+ unsigned int *completed);
struct ath10k_peer *ath10k_peer_find(struct ath10k *ar, int vdev_id,
const u8 *addr);
--
2.1.4
On 30 March 2016 at 17:28, Ben Greear <[email protected]> wrote:
> On 03/30/2016 02:22 AM, Michal Kazior wrote:
>>
>> On 29 March 2016 at 17:54, Ben Greear <[email protected]> wrote:
>>>
>>> On 03/29/2016 12:49 AM, Michal Kazior wrote:
>>>
>>>>> if you are getting a pure codel result of 160ms, that means the
>>>>> implementation is broken. But I think (after having read your
>>>>> description twice), the baseline result today of 160ms of queuing was
>>>>> with a fq_codel *qdisc* doing the work on top of huge buffers,
>>>>
>>>>
>>>>
>>>> Yes. The 160ms is with fq_codel qdisc with ath10k doing DQL at 6mbps.
>>>> Without DQL ath10k would clog up all tx slots (1424 of them) with
>>>> frames. At 6mbps you typically want/need a handful (5-10) of frames to
>>>> be queued.
>>>
>>>
>>>
>>> Have you actually verified you can use all tx slots?
>>
>>
>> It works in most cases. I guess you're suspecting some of your
>> tx(flushing?) problems might be induced by overcommiting?
>>
>>> The way the
>>> firmware uses it's tx buffers I think you may not be able to actually
>>> do that...and in practice, you will get a lot fewer usable tx-buffers
>>> than configured....
>>
>>
>> Could be, e.g. I'm aware management frames are kind of a special case
>> in recent firmware revisions.
>>
>> What would/do you expect firmware would/will do when we overcommit?
>> The driver does advertise number of HTT tx slots so I would expect it
>> to work fine if it didn't crash during boot.
>
>
> The firmware will return something like tx-dropped immediately. The reason
> is that the firmware keeps more than one internal priority queue, and in
> general, reserves
> some of the tx-descriptors for high priority.
>
> So, you never see tx-queues completely full in the driver, so tx queues are
> not stopped farther up the stack.
>
> Possibly I am confused about some of this, so I'm quite curious if you ever
> see
> tx-queues determined to be full in the ath10k driver.
I haven't analyzed it this much. Nevertheless it's good to know we
might be overcommiting on the HTT Tx. One more reason to use DQL
and/or schedule tx in a smarter way.
Michał
On 03/30/2016 02:22 AM, Michal Kazior wrote:
> On 29 March 2016 at 17:54, Ben Greear <[email protected]> wrote:
>> On 03/29/2016 12:49 AM, Michal Kazior wrote:
>>
>>>> if you are getting a pure codel result of 160ms, that means the
>>>> implementation is broken. But I think (after having read your
>>>> description twice), the baseline result today of 160ms of queuing was
>>>> with a fq_codel *qdisc* doing the work on top of huge buffers,
>>>
>>>
>>> Yes. The 160ms is with fq_codel qdisc with ath10k doing DQL at 6mbps.
>>> Without DQL ath10k would clog up all tx slots (1424 of them) with
>>> frames. At 6mbps you typically want/need a handful (5-10) of frames to
>>> be queued.
>>
>>
>> Have you actually verified you can use all tx slots?
>
> It works in most cases. I guess you're suspecting some of your
> tx(flushing?) problems might be induced by overcommiting?
>
>> The way the
>> firmware uses it's tx buffers I think you may not be able to actually
>> do that...and in practice, you will get a lot fewer usable tx-buffers
>> than configured....
>
> Could be, e.g. I'm aware management frames are kind of a special case
> in recent firmware revisions.
>
> What would/do you expect firmware would/will do when we overcommit?
> The driver does advertise number of HTT tx slots so I would expect it
> to work fine if it didn't crash during boot.
The firmware will return something like tx-dropped immediately. The reason
is that the firmware keeps more than one internal priority queue, and in general, reserves
some of the tx-descriptors for high priority.
So, you never see tx-queues completely full in the driver, so tx queues are
not stopped farther up the stack.
Possibly I am confused about some of this, so I'm quite curious if you ever see
tx-queues determined to be full in the ath10k driver.
Thanks,
Ben
--
Ben Greear <[email protected]>
Candela Technologies Inc http://www.candelatech.com
Re-posting text only as it was blocked by most mailing list servers:
The original attachment can be fetched at:
http://kazikcz.github.io/dl/2016-04-01-flent-ath10k-dql.tar.gz
On 25 March 2016 at 10:55, Michal Kazior <[email protected]> wrote:
> On 25 March 2016 at 10:39, Michal Kazior <[email protected]> wrote:
>> This implements a very naive dynamic queue limits
>> on the flat HTT Tx. In some of my tests (using
>> flent) it seems to reduce induced latency by
>> orders of magnitude (e.g. when enforcing 6mbps
>> tx rates 2500ms -> 150ms). But at the same time it
>> introduces TCP throughput buildup over time
>> (instead of immediate bump to max). More
>> importantly I didn't observe it to make things
>> much worse (yet).
>>
>> Signed-off-by: Michal Kazior <[email protected]>
>> ---
>>
>> I'm not sure yet if it's worth to consider this
>> patch for merging per se. My motivation was to
>> have something to prove mac80211 fq works and to
>> see if DQL can learn the proper queue limit in
>> face of wireless rate control at all.
>>
>> I'll do a follow up post with flent test results
>> and some notes.
>
> Here's a short description what-is-what test naming:
> - sw/fq contains only txq/flow stuff (no scheduling, no txop queue limits)
> - sw/ath10k_dql contains only ath10k patch which applies DQL to
> driver-firmware tx queue naively
> - sw/fq+ath10k_dql is obvious
> - sw/base today's ath.git/master checkout used as base
> - "veryfast" tests TCP tput to reference receiver (4 antennas)
> - "fast" tests TCP tput to ref receiver (1 antenna)
> - "slow" tests TCP tput to ref receiver (1 *unplugged* antenna)
> - "fast+slow" tests sharing between "fast" and "slow"
> - "autorate" uses default rate control
> - "rate6m" uses fixed-tx-rate at 6mbps
> - the test uses QCA9880 w/ 10.1.467
> - no rrul tests, sorry Dave! :)
>
> \
> Observations / conclusions:
> - DQL builds up throughput slowly on "veryfast"; in some tests it
> doesn't get to reach peak (roughly 210mbps average) because the test
> is too short
>
> - DQL shows better latency results in almost all cases compared to
> the txop based scheduling from my mac80211 RFC (but i haven't
> thoroughly looked at *all* the data; I might've missed a case where it
> performs worse)
>
> - latency improvement seen on sw/ath10k_dql @ rate6m,fast compared to
> sw/base (1800ms -> 160ms) can be explained by the fact that txq AC
> limit is 256 and since all TCP streams run on BE (and fq_codel as the
> qdisc) the induced txq latency is 256 * (1500 / (6*1024*1024/8.)) / 4
> = ~122ms which is pretty close to the test data (the formula ignores
> MAC overhead, so the latency in practice is larger). Once you consider
> the overhead and in-flight packets on driver-firmware tx queue 160ms
> doesn't seem strange. Moreover when you compare the same case with
> sw/fq+ath10k_dql you can clearly see the advantage of having fq_codel
> in mac80211 software queuing - the latency drops by (another) order of
> magnitude because now incomming ICMPs are treated as new, bursty flows
> and get fed to the device quickly.
>
> - slow+fast case still sucks but that's expected because DQL hasn't
> been applied per-station
>
> - sw/fq has lower peak throughput ("veryfast") compared to sw/base
> (this actually proves current - and very young least to say - ath10k
> wake-tx-queue implementation is deficient; ath10k_dql improves it and
> sw/fq+ath10k_dql climbs up to the max throughput over time)
>
>
> To sum things up:
> - DQL might be able to replace the explicit txop queue limiting
> (which requires rate control info)
> - mac80211 fair queuing works
>
>
> A few plots for quick and easy reference:
>
> http://imgur.com/a/TnvbQ
Michał