* when pulling frames off of the TID queue, the ATH_TID_REMOVE()
macro decrements the axq_depth field. So don't do it twice.
* in ath_tx_comp_cleanup_aggr(), bf wasn't being reset to bf_first
before walking the buffer list to complete buffers; so those buffers
will leak.
I can 100% reliably trigger this on TID 1 traffic by using iperf -S 32
<client fields> to create traffic that maps to TID 1.
The reference driver doesn't do this check.
* Delete this debugging print - I used it when debugging the initial
TX descriptor chaining code. It now works, so let's toss it.
It just confuses people if they enable TX descriptor debugging as they
get two slightly different versions of the same descriptor.
* Indenting.
My changed had some rather significant behavioural changes to throughput.
The two issues I noticed:
* With if_start and the ifnet mbuf queue, any temporary latency
would get eaten up by some mbufs being queued. With ath_transmit()
queuing things to ath_buf's, I'd only get 512 TX buffers before I
couldn't queue any further frames.
* There's also some non-zero latency involved with TX being pushed
into a taskqueue via direct dispatch. Any time the scheduler didn't
immediately schedule the ath TX task would cause extra latency.
Various 1ge/10ge drivers implement both direct dispatch (if the TX
lock can be acquired) and deferred task transmission (if the TX lock
can't be acquired), with frames being pushed into a drbd queue.
I'll have to do this at some point, but until I figure out how to
deal with 802.11 fragments, I'll have to wait a while longer.
So what I saw:
* lots of extra latency, specially under load - if the taskqueue
wasn't immediately scheduled, things went pear shaped;
* any extra latency would result in TX ath_buf's taking their sweet time
being replenished, so any further calls to ath_transmit() would drop
mbufs.
* .. yes, there's no explicit backpressure here - things are just dropped.
Eek.
With this, the general performance has gone up, but those subtle if_start()
related race conditions are back. For some reason, this is doubly-obvious
with the AR5416 NIC and I don't quite understand why yet.
There's an unrelated issue with AR5416 performance in STA mode (it's
fine in AP mode when bridging frames, weirdly..) that requires a little
further investigation. Specifically - it works fine on a Lenovo T40
(single core CPU) running a March 2012 9-STABLE kernel, but a Lenovo T60
(dual core) running an early November 2012 kernel behaves very poorly.
The same hardware with an AR9160 or AR9280 behaves perfectly.
the separate ath0 TX taskq.
Whilst here, make sure that the TX software scheduler is also
running out of the TX task, rather than the ath0 taskqueue.
Make sure that the tx taskqueue is blocked/unblocked as necessary.
This allows for a little more parallelism on multi-core machines,
as well as (eventually) supporting a higher task priority for TX
tasks, allowing said TX task to preempt an already running RX or
TX completion task.
Tested:
* AR5416, AR9280 hostap and STA modes
This is easily possible now that the TX is protected by a single
lock, rather than a per-TXQ (and thus per-TID) lock.
Only set CLRDMASK if none of the destinations are filtered.
This likely will need some tuning when it comes time to do UASPD/PS-POLL
TX, however at that point it should be manually set anyway.
Tested:
* AR9280, STA mode
TODO:
* More thorough testing in AP mode
* test other chipsets, just to be safe/sure.
if_start().
This removes the overlapping data path TX from occuring, which
solves quite a number of the potential TX queue races in ath(4).
It doesn't fix the net80211 layer TX queue races and it doesn't
fix the raw TX path yet, but it's an important step towards this.
This hasn't dropped the TX performance in my testing; primarily
because now the TX path can quickly queue frames and continue
along processing.
This involves a few rather deep changes:
* Use the ath_buf as a queue placeholder for now, as we need to be
able to support queuing a list of mbufs (ie, when transmitting
fragments) and m_nextpkt can't be used here (because it's what is
joining the fragments together)
* if_transmit() now simply allocates the ath_buf and queues it to
a driver TX staging queue.
* TX is now moved into a taskqueue function.
* The TX taskqueue function now dequeues and transmits frames.
* Fragments are handled correctly here - as the current API passes
the fragment list as one mbuf list (joined with m_nextpkt) through
to the driver if_transmit().
* For the couple of places where ath_start() may be called (mostly
from net80211 when starting the VAP up again), just reimplement
it using the new enqueue and taskqueue methods.
What I don't like (about this work and the TX code in general):
* I'm using the same lock for the staging TX queue management and the
actual TX. This isn't required; I'm just being slack.
* I haven't yet moved TX to a separate taskqueue (but the taskqueue is
created); it's easy enough to do this later if necessary. I just need
to make sure it's a higher priority queue, so TX has the same
behaviour as it used to (where it would preempt existing RX..)
* I need to re-review the TX path a little more and make sure that
ieee80211_node_*() functions aren't called within the TX lock.
When queueing, I should just push failed frames into a queue and
when I'm wrapping up the TX code, unlock the TX lock and
call ieee80211_node_free() on each.
* It would be nice if I could hold the TX lock for the entire
TX and TX completion, rather than this release/re-acquire behaviour.
But that requires that I shuffle around the TX completion code
to handle actual ath_buf free and net80211 callback/free outside
of the TX lock. That's one of my next projects.
* the ic_raw_xmit() path doesn't use this yet - so it still has
sequencing problems with parallel, overlapping calls to the
data path. I'll fix this later.
Tested:
* Hostap - AR9280, AR9220
* STA - AR5212, AR9280, AR5416
I couldn't think of a way to maintain the hardware TXQ locks _and_ layer
on top of that per-TXQ software queuing and any other kind of fine-grained
locks (eg per-TID, or per-node locks.)
So for now, to facilitate some further code refactoring and development
as part of the final push to get software queue ps-poll and u-apsd handling
into this driver, just do away with them entirely.
I may eventually bring them back at some point, when it looks slightly more
architectually cleaner to do so. But as it stands at the present, it's
not really buying us much:
* in order to properly serialise things and not get bitten by scheduling
and locking interactions with things higher up in the stack, we need to
wrap the whole TX path in a long held lock. Otherwise we can end up
being pre-empted during frame handling, resulting in some out of order
frame handling between sequence number allocation and encryption handling
(ie, the seqno and the CCMP IV get out of sequence);
* .. so whilst that's the case, holding the lock for that long means that
we're acquiring and releasing the TXQ lock _inside_ that context;
* And we also acquire it per-frame during frame completion, but we currently
can't hold the lock for the duration of the TX completion as we need
to call net80211 layer things with the locks _unheld_ to avoid LOR.
* .. the other places were grab that lock are reset/flush, which don't happen
often.
My eventual aim is to change the TX path so all rejected frame transmissions
and all frame completions result in any ieee80211_free_node() calls to occur
outside of the TX lock; then I can cut back on the amount of locking that
goes on here.
There may be some LORs that occur when ieee80211_free_node() is called when
the TX queue path fails; I'll begin to address these in follow-up commits.
* upon setup, tell the alq code what the chip information is.
* add TX/RX path logging for legacy chips.
* populate the tx/rx descriptor length fields with a best-estimate.
It's overly big (96 bytes when AH_SUPPORT_AR5416 is enabled)
but it'll do for now.
Whilst I'm here, add CURVNET_RESTORE() here during probe/attach as a
partial solution to fixing crashes during attach when the attach fails.
There are other attach failures that I have to deal with; those'll come
later.
This was broken by me when merging the 802.11n aggregate descriptor chain
setup with the default descriptor chain setup, in preparation for supporting
AR9380 NICs.
The corner case here is quite specific - if you queue an aggregate frame
with >1 frames in it, and the last subframe has only one descriptor making
it up, then that descriptor won't have the rate control information
copied into it. Look at what happens inside ar5416FillTxDesc() if
both firstSeg and lastSeg are set to 1.
Then when ar5416ProcTxDesc() goes to fill out ts_rate based on the
transmit index, it looks at the rate control fields in that descriptor
and dutifully sets it to be 0.
It doesn't happen for non-aggregate frames - if they have one descriptor,
the first descriptor already has rate control info.
I removed the call to ath_hal_setuplasttxdesc() when I migrated the
code to use the "new" style aggregate chain routines from the HAL.
But I missed this particular corner case.
This is a bit inefficient with MIPS boards as it involves a few redundant
writes into non-cachable memory. I'll chase that up when it matters.
Tested:
* AR9280 STA mode, TCP iperf traffic
* Rui Paulo <rpaulo@> first reported this and has verified it on
his AR9160 based AP.
PR: kern/173636
This happens during a scan in STA mode; any queued data frames will
be power save queued but as there's no TIM in STA mode, it panics.
This was introduced by me when I disabled my driver-aware power save
handling support.
events.
This is primarily for the TX EDMA and TX EDMA completion. I haven't yet
tied it into the EDMA RX path or the legacy TX/RX path.
Things that I don't quite like:
* Make the pointer type 'void' in ath_softc and have if_ath_alq*()
return a malloc'ed buffer. That would remove the need to include
if_ath_alq.h in if_athvar.h.
* The sysctl setup needs to be cleaned up.
the non-aggregate path.
I "cheated" by using some TX setup code in our HAL that isn't present
in the atheros HAL (or Linux ath9k.)
The old path for forming aggregates was:
* setup the rate control in the first descriptor;
* call chaintxdesc() on all the frames;
* call setupfirsttxdesc() on the first descrpitor in the first
frame;
* call setuplasttxdesc() on the last descriptor in the last frame.
The new path for forming aggregates looks like the non-aggregate path:
* call setuptxdesc() on the first descriptor in the first frame;
* setup the rate control in the first descriptor;
* call filltxdesc() on each descriptor in the frame;
* if it's an aggregate - call set11n_aggr_{first, middle, last} as
appropriate (see the code for a description of what is "appropriate".)
Now, this is done primarily for the AR9300 HAL - it doesn't implement
the first set of aggregate functions. It just has the older methods
and the "first/middle/last" aggregate methods. So, let's convert the
code to use these.
Note: the AR5416 HAL in FreeBSD had that code (from me, a while ago)
and a previous commit brought it up to behave the same as the AR9300
HAL routines.
There's some further tidyups to be done - specifically, avoid doing
multiple calls to the 11n descriptor functions. I shouldn't call
clr11n_aggr(), then set11n_aggr_middle(), then also set11n_aggr_first().
On (at least MIPS) the TX descriptors are in non-cachable memory and
this will cause multiple slow writes.
I'll debug/tidy that up in a future commit.
Tested:
* AR9280, STA
* AR9280/AR9160, AP
* AR9380, STA (using a local, closed source HAL, sorry!)
I've tried serialising TX using queues and such but unfortunately
due to how this interacts with the locking going on elsewhere in the
networking stack, the TX task gets delayed, resulting in quite a
noticable throughput loss:
* baseline TCP for 2x2 11n HT40 is ~ 170mbit/sec;
* TCP for TX task in the ath taskq, with the RX also going on - 80mbit/sec;
* TCP for TX task in a separate, second taskq - 100mbit/sec.
So for now I'm going with the Linux wireless stack approach - lock tx
early. The linux code does in the wireless stack, before the 802.11
state stuff happens and before it's punted to the driver.
But TX locking needs to also occur at the driver layer as the TX
completion code _also_ begins to drain the ifnet TX queue.
Whilst I'm here, add some KTR traces for the TX path.
Note:
* This really should be done at the net80211 layer (as well, at least.)
But that'll have to wait for a little more thought to happen.
the power save queue.
* introduce some new ATH_NODE lock protected fields, tracking the
net80211 psq and TIM state;
* when doing buffer transitions - ie, when sending and completing
buffers - check the state of the SWQ and update the TIM appropriately.
* when clearing the TIM bit, if the SWQ is not empty then delay clearing
it.
This is racy, but it's no less racy than the current net80211 power
save queue management code. Specifically, with multiple TX threads,
it's quite plausible that parallel state updates will race and the
TIM will be left in an inconsistent state. I'll address that in
a follow-up commit.
fragment rate lookups correctly, add a comment describing exactly that.
The assumption in the fragment duration code is the duration of the next
fragment will match the rate used by the current fragment. But I think
a rate lookup is being done for _each_ fragment. For older pre-sample
rate control this would almost always be the case, but for sample
it may be incorrect more often then correct.
the ATH_TXQ_* macros.
* Introduce the new macros;
* rename the TID queue and TID filtered frame queue so the compiler
tells me I'm using the wrong macro.
These should correspond 1:1 to the existing code.
net80211 node power save state.
* Add an ATH_NODE_UNLOCK_ASSERT() check
* Add a new node field - an_is_powersave
* Pause/unpause the queue based on the node state
* Attempt to handle net80211 concurrency issues so the queue
doesn't get paused/unpaused more than once at a time from
the net80211 power save code.
Whilst here (and breaking my usual rule), set CLRDMASK when a queue
is unpaused, regardless of whether the queue has some pending traffic.
This means the first frame from that TID (now or later) will hvae
CLRDMASK set.
Also whilst here, bump the swretrymax counters whenever the
filtered frames code expires a frame. Again, breaking my rule, but
this is just a statistics thing rather than a functional change.
This doesn't fix ps-poll (but it doesn't break it too much worse
than it is at the present) or correcting the TID updates.
That's next on the list.
Tested:
* AR9220 AP (Atheros AP96 reference design)
* Macbook Pro and LG Optimus 1 Android phone, both setting
and clearing power save state (but not using PS-POLL.)
things like EAPOL frames make it out.
After a whole bunch of hacking/testing, I discovered that they weren't
being early-dropped by the stack (but I should look at ensuring that
later..) but were even making to the hardware transmit queue.
They were mostly even being received by the remote end. However, the
remote end was completely ignoring them.
This didn't happen under 150-170MBit TCP tests as I'm guessing the TX
queue stayed very busy and the STA didn't do any scanning. However, when
doing 100Mbit/s of TCP traffic, the STA would do background scanning -
which involves it coming in and out of powersave mode with the AP.
Now, this is a total and utter hack around the real problems, which are:
* I need to implement proper power save handling and integrate it into
the filtered frames support, so the driver/stack doesn't send frames
whilst the station is actually in sleep;
* .. but frames were actually making it to the STA (macbook pro) and
the AP did receive an ACK; but a tcpdump on the receiving side showed
the EAPOL frame never made it. So the stack was dropping it for
some reason;
* Importantly - the EAPOL frames are currently going into the non-QoS
TID, which maps to the BE queue and is susceptible to that queue being
busy doing other things, but;
* There's other traffic going on in the non-QoS TID from other contexts
when scanning is going on and it's possible there's some races causing
sequence number/IV issues, but;
* Importantly importantlly, I think the interaction with TID 16 multicast
traffic in power save mode is causing issues - since I -believe- the
sequence number space being used by the EAPOL frames on TID 16 overlaps
with the multicast frames that have sequence numbers allocated and
are then stuffed on the cabq. Since with EAPOL frames being in TID 16
and queued to the BE queue, it's going to be waiting to be serviced
with all of the aggregate traffic going on - and if the CABQ gets
emptied beforehand, those TID 16 multicast frames with sequence numbers
will go out beforehand.
Now, there's quite likely a bunch of "stuff happening slightly out of
sequence" going on due to the nature of the TX path (read: lots of
overlapping and concurrent ath_start() and ath_raw_xmit() calls going
on, sigh) but I thought I had caught them all and stuffed each TID TX
behind a lock (that lasted as long as it needed to in order to get
the frame onto the relevant destination queue - thus keeping things
in order.)
Unfortunately the last problem is the big one and I'm going to stare at
it some more. If it _is_
So this is a work around for now to ensure that EAPOL frames actually
make it out before any other stuff in the non-QoS TID and HOPEFULLY
before the CABQ gets active.
I'm now going to spend a little time in the TX path figuring out exactly
why the sender is rejecting things. There's two (well, three if you count
EAPOL contents invalid) possibilities:
* The sequence number is out of order (ie, something else like the multicast
traffic on CABQ) is going out first on TID 16;
* The CCMP IV is out of order (similar to above - but less likely, as the
TX key for multicast traffic is different to unicast traffic);
* EAPOL contents strangely invalid.
AP: Ubiquiti RSPRO, AR9160/AR9220 NICs
STA: Macbook Pro, Broadcom 11n NIC
lock may be held.
Kim reported that the TID lock wasn't held when ath_tx_update_clrdmask()
was called. Well, the underlying hardware TXQ for that TID.
I'm betting it's the cabq stuff. ath_tx_xmit_normal() can be called
for both real and software cabq. For software cabq, the real destination
txq is different to the txq. So, the lock check will fail.
Reported by: Kim Culhan <w8hdkim@gmail.com>
This should eventually be unified with ATH_DEBUG() so I can get both
from one macro; that may take some time.
Add some new probes for TX and TX completion.
it's disabled.
The previous commit to enable CLRDMASK setting didn't do it at all
correctly for non-aggregate sessions - so the CLRDMASK bit would be
cleared and never re-set.
* move ath_tx_update_clrdmask() to be called by functions that setup
descriptors and queue frames to the hardware, rather than scattered
everywhere.
* Force CLRDMASK to be set on all non-aggregate session frames being
transmitted.
* Use ath_tx_normal_comp() now on non-aggregate sessoin frames
that are queued via ath_tx_xmit_normal(). That way the TID hwq is
updated and they can trigger (eventual) filter frame queue resets
and software retransmits.
There's still a bit more work to do in this area to reverse the silly
short-sightedness on my part, however it's likely going to be better
to fix this now than just reverting the patch.
Thanks to people on the freebsd-wireless@ mailing list for promptly
pointing this out.
frames to occur.
* Create a new function which will set the bf_flags CLRDMASK bit
if required.
* For raw frames, always set CLRDMASK.
* For BAR, ADDBA frames, always set CLRDMASK.
* For everything else, check if CLRDMASK needs to be set before
calling tx_setds() or tx_setds11n().
* When unpausing a queue or drain/resetting it, set tid->clrdmask=1
just to ensure traffic starts flowing.
What I need to do:
* Modify that function to _clear_ the CLRDMASK if it's not required,
or retried frames may have CLRDMASK set when they don't need to.
(Which isn't a huge deal, but..)
Whilst I'm here:
* ath_tx_normal_xmit() should really act like the AMPDU session TX
functions - any incomplete frames will end up being assigned
ath_tx_normal_comp() which will decrement tid->hwq_depth - but that
won't have been incremented.
So whilst I'm here, add a comment to do that.
* Fix the debug print function to be slightly clearer about things;
it's not a good sign when I can't interpret my own debugging output.
I've done some testing on AR9280/AR5416/AR9160 STA and AP modes.
stack.
There are unfortunately quite a few odd cases in BAR TX and BAR TX
retransmission that I haven't yet fully diagnosed. So for now, add
this work-around so the resume() function isn't called too often,
decrementing pause to -1 (and causing things to stay paused.)
is done.
The aggregate path was definitely accessing 'ts' before it was actually
being assigned.
This had the side effect of over-filtering frames, since occasionally that
bit would be '1'.
Whilst here, do the same thing in the non-aggregate completion function -
as calling the filter function may also invalidate bf.
Pointy hat to: adrian, for not noticing this over many, many code reviews.
The hardware can optionally "filter" frames if successive transmissions
to a given node (ie, "entry in the keycache") fail. That way the hardware
can implement a kind of early abort of all the other frames queued to
that destination, rather than simply trying to TX each frame to that
destination (and failing.)
The background:
* If a frame comes back as being filtered, the hardware didn't try to
TX it (or it was outside the TX burst opportunity.) So, take it as a hint
that some (but not all, see below) frames to the destination may be
filtered.
* If the CLRDMASK bit is set in a TX descriptor, the "filter to this
destination" bit in the keycache entry is cleared and TX to that host
will be unconditionally retried.
* Right now everything has the CLRDMASK bit set, so filtered frames
tend to be aggregates and frames that fall outside of the WME burst
window. It was a bit worse in the past as I had messed up the TX
flags and CLRDMASK wasn't being set on aggregate frames.
The annoying bits:
* It's easy (ish) to do for aggregate session frames - firstly, they
can be retried in any order as long as they're within the BAW, and
there's already a bunch of infrastructure tracking how many frames
the TID has queued to the hardware (tid->hwq_depth.) However, for
frames that bypassed the software queue, hwq_depth doesn't get
incremented. I'll fix that in a subsequent commit.
* For non-aggregate session frames, the only retries that can occur
are ones for sequence numbers that hvaen't successfully been TXed yet.
Since there's no re-ordering going on in non-aggregate sessions, if any
subsequent seqno frames make it out, any filtered frames before that
seqno need to be dropped.
Hence why this initially is just for aggregate session frames.
* Since there may be intermediary frames to the destination that
have CLRDMASK set - for example, any directly dispatched management
frames to that destination - it's possible that there will be some
filtered frames followed up by some non filtered frames. Thus,
it can't be assumed that once you see a filtered frame for the given
destination node, all subsequent frames for all TIDs will be filtered.
Ok, with that in mind:
* Create a per-TID filtered frame queue for frames that the hardware
returns as filtered.
* Track filtered frames per-tid, rather than per-node. It just makes
the locking much easier.
* When a filtered frame appears in the completion function, the node
transitions to "filtered", and all subsequent completed error frames
(filtered or otherwise) are put on the filtered frame queue. The TID
is paused once (during the transition from non-filtered to filtered).
* If a filtered frame retry count exceeds SWMAX_RETRIES, a BAR should be
sent.
* Once all the frames queued to the hardware for the given filtered frame
TID, transition back from filtered frame to non-filtered frame, which
means pre-pending all the filtered frames onto the head of the software
queue, clearing the filtered frame state and unpausing the TID.
Things get quite hairy around handling completion (aggr, non-aggr, norm,
direct-dispatched frames to a hardware queue); whether it's an "error",
"cleanup" or "BAR" state as well as filtered, which order to do things
in (eg do filtered BEFORE checking for BAR, as the filter completion
may be needed to actually transmit a BAR frame.)
This work has definitely reminded me that I have to tidy up all the locking
and remove some of the ridiculous lock/unlock/lock/unlock going on in the
completion functions.
It's also reminded me that I should really split out TID versus hardware TXQ
locking, even if the underlying locking is still the destination hardware TXQ.
Finally, this is all pre-requisite for working on AP mode power save support
(PS-POLL, uAPSD) as well as improving performance to misbehaving nodes (as
they can transition into filter mode, stopping any TX until everything has
caught up.)
Finally (ish) - this should also be done for non-aggregate sessions as
there are still plenty of laptops and mobile devices that don't speak
802.11n but do wish for stable, useful power save AP support where packets
aren't simply dropped. This requires software retransmission for
non-aggregate sessions to be implemented, which includes the caveats I've
mentioned above.
Finally finally - this doesn't yet do anything about the CLRDMASK bit in the
TX descriptor. That's still unconditionally set to 1. I'll debug the
current work (mostly ensuring I haven't busted up the hairy transitions
between BAR, filtered, error (all frames in an aggregate failing) and
cleanup (when transitioning from aggregation -> non-aggregation.))
Finally finally finally - this is all original work by yours truely, rather
than ported from the Atheros internal driver codebase or Linux ath9k.
Tested:
* AR9280, AR5416 in STA mode
* AR9280, AR9130 in hostap mode
* Lots and lots of iperf testing in very marginal and non-marginal conditions,
complete with inducing filtered frames + BAR TX conditions.
ath_buf and when forming a non-aggregate frame.
The non-11n setds function is called when TXing aggregate frames (and
yes, I should fix this!) and the non-11n TX aggregation code doesn't clear
the delimiter field. I figure it's nicer to do that.
with the correct configuration.
Occasionally an aggregate TX would fail and the first frame would be
retransmitted as a non-AMPDU frame. Since bfs_aggr=1 and bfs_nframes > 1
(from the previous AMPDU attempt), the aggr completion function would be
called and be very confused about what's going on.
Noticed by: Kim <w8hdkim@gmail.com>
PR: kern/171394
sizeof(struct ath_desc). This isn't correct for EDMA TX descriptors.
This popped up during iperf tests. Ping tests never created frames that
had enough segments to overflow into a second descriptor. However,
an iperf TCP test would do that after a few seconds; the second descriptor
would almost always certainly have garbage.
Tested:
* AR9380, STA mode
* AR9280, STA mode (802.11n TX, legacy TX)
is marked correctly.
The existing logic assumed that the first descriptor is i == 0, which
doesn't hold for EDMA TX. In this instance, the first time filltxdesc()
is called can be up to i == 3.
So for a two-buffer descriptor:
* firstSeg is set to 0;
* lastSeg is set to 1;
* the ath_hal_filltxdesc() code will treat it as the last segment in
a descriptor chain and blank some of the descriptor fields, causing
the TX to stop.
When firstSeg is set to 1 (regardless of lastSeg), it overrides the
lastSeg setting. Thus, ath_hal_filltxdesc() won't blank out these
fields.
Tested: AR9380, STA mode. With this, association is successful.
