[ath9k-devel] How to lock AMPDU length at a specific value?

[Ali Abedi <a2abedi@uwaterloo.ca>]

Thanks for all the replies.
Sorry for not mentioning that I actually saturate the link. I use iperf 
and I set the application data rate
to something way more that the mac throughput. The strange thing is that 
not all A-MPDUs are at the maximum size.

Here is some results I got from the driver for different max A-MPDU 
sizes (High app data rate).

left column is #frames and the column is #bad-frames
Mac data rate = 65 Mbps fixed.
App data rate = 100 Mbps

I directly print these stats from xmit.c in ath_tx_complete_agg(), after 
the call to function ath_tx_count_frames().
I print nframes and nbad variables.

max A-mpdu size = 10 * 1550 B
10    0
10    0
10    0
10    0
10    0
10    0
10    0
10    0
10    0

Everything is fine all A-MPDUs have 10 frames
-----------------------
max A-mpdu size = 20 * 1550 B
20    0
20    0
20    0
9    0
20    0
20    0
1    0
20    0
20    0
8    0
20    0

Sometimes a-mpdus with fewer frames than 20
-----------------------
Max A-mpdu size = 32 * 1550 B
8    0
32    0
2    0
32    32
3    0
32    0
1    0
32    0
4    4
1    0
32    32

It happens even more frequently.

Is there a solution to this problem?

Thank you,
Ali


On 14-01-22 02:08 AM, Kamran Nishat wrote:
> Yeah,
> My initial  premise was  that u have saturated traffic from upper 
> layers. But now I think u have some application level requirements 
> (data rate is less than max PHY rate).
> In this case I would advise you to add wait in mac80211. Because as 
> far as I know ath9k driven by its calls and calls by driver.
>
> Regards,
> kamran
>
>
> On Wed, Jan 22, 2014 at 10:19 AM, Shinnazar <seytnazarovsho@ynu.ac.kr 
> <mailto:seytnazarovsho@ynu.ac.kr>> wrote:
>
>     Hi Ali,
>
>     If I were you, I would try to make the Software queue always full
>     of frames and then specify ampdu lenfth in ath_tx_form_aggr().
>
>     BR,
>     Shinnazar
>
>         --- Original Message ---
>         *From : *Ali Abedi< a2abedi@uwaterloo.ca
>         <mailto:a2abedi@uwaterloo.ca> >
>         *To : *ath9k-devel at venema.h4ckr.net
>         <mailto:ath9k-devel@venema.h4ckr.net>
>         *CC : *
>         *Sent : *2014-01-22 06:40:18
>         *Subject : *Re: [ath9k-devel] Fwd: How to lock AMPDU length at
>         a specific value?
>
>
>         _______________________________________________
>         ath9k-devel mailing list
>         ath9k-devel at lists.ath9k.org  <mailto:ath9k-devel@lists.ath9k.org>
>         https://lists.ath9k.org/mailman/listinfo/ath9k-devel
>
>         Using a constant rate does not help (I am already doing this).
>         When I set the limit to 20 for example, I get any number between
>         1 to 20 for the number of aggregated frames. This is probably
>         because when we want to start the transmission
>         we don't always have 20 frames to aggregate so the card
>         aggregates all it already has
>         in the queue ready for transmission. So how can we wait to
>         have 20 frames ready for transmission so that
>         all aggregate frames carry exactly 20 frames (constant rate)?
>
>         Thank you,
>         Ali
>
>
>         On 21/01/2014 15:59, Kamran Nishat wrote:
>>
>>
>>
>>
>>         do it at a fix rate  (1st check if duration of packet is less
>>         tahn 4ms for ur MCS) and with nearly zero noise losses.
>>
>>         Kamran
>>
>>
>>         On Wed, Jan 22, 2014 at 1:54 AM, Ali Abedi
>>         <a2abedi at uwaterloo.ca <mailto:a2abedi@uwaterloo.ca>> wrote:
>>
>>             These mostly determine the MAX AMPDU length. I also want
>>             to determine the minimum length, so
>>             that I can set min=max and lock the AMPDU length.
>>
>>             Thank you,
>>             Ali
>>
>>             On 21/01/2014 15:07, Kamran Nishat wrote:
>>>             As far as i know AMPDU length is determined by 3
>>>             constraints. Firs maximum AMPDU length. second blockAck
>>>             window (if there were losses then this will play a
>>>             role).  Third is Max air time of the AMPDU which is 4ms
>>>             for some domain constraints. this comes into play MCS is
>>>             low and packet duration gets more than 4ms. See
>>>             following function in xmit.c for details
>>>             ath_tx_form_aggr  <http://lxr.free-electrons.com/ident?i=ath_tx_form_aggr>  
>>>
>>>
>>>             On Tue, Jan 21, 2014 at 11:49 PM, Ali Abedi
>>>             <a2abedi at uwaterloo.ca <mailto:a2abedi@uwaterloo.ca>> wrote:
>>>
>>>                 Hello,
>>>
>>>                 I have seen questions regarding the length of an
>>>                 AMPDU and how to change
>>>                 the maximum AMPDU length.
>>>                 However, I require to lock the AMPDU length at a
>>>                 specific value.
>>>                 Changing the max length does not guarantee
>>>                 that all AMPDUs have a fixed length, it can be
>>>                 anything between 1 to max
>>>                 based on the rate of arrival of new frames.
>>>                 Is there a mechanism to force the card to wait to
>>>                 have enough frames so
>>>                 that all AMPDUs have a fixed length that we specify?
>>>                 In other words, I
>>>                 need all AMPDUs to aggregate X full length frames.
>>>
>>>                 Thank you,
>>>                 Ali
>>>
>>>                 _______________________________________________
>>>                 ath9k-devel mailing list
>>>                 ath9k-devel at lists.ath9k.org
>>>                 <mailto:ath9k-devel@lists.ath9k.org>
>>>                 https://lists.ath9k.org/mailman/listinfo/ath9k-devel
>>>
>>>
>>
>>
>>
>>
>>
>>         _______________________________________________
>>         ath9k-devel mailing list
>>         ath9k-devel at lists.ath9k.org  <mailto:ath9k-devel@lists.ath9k.org>
>>         https://lists.ath9k.org/mailman/listinfo/ath9k-devel
>
>
>
>
>
>
>
>     _______________________________________________
>     ath9k-devel mailing list
>     ath9k-devel at lists.ath9k.org <mailto:ath9k-devel@lists.ath9k.org>
>     https://lists.ath9k.org/mailman/listinfo/ath9k-devel
>
>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.ath9k.org/pipermail/ath9k-devel/attachments/20140122/e9b7b211/attachment.htm