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Date:   Wed, 18 Sep 2019 18:29:37 +0800
From:   Yibo Zhao <yiboz@codeaurora.org>
To:     =?UTF-8?Q?Toke_H=C3=B8iland-J=C3=B8rgensen?= <toke@redhat.com>
Cc:     ath10k@lists.infradead.org, linux-wireless@vger.kernel.org
Subject: Re: [PATCH V2 3/4] mac80211: fix low throughput in multi-clients
 situation
In-Reply-To: <874l19j56n.fsf@toke.dk>
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 <874l19j56n.fsf@toke.dk>
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On 2019-09-18 17:59, Toke Høiland-Jørgensen wrote:
> Yibo Zhao <yiboz@codeaurora.org> writes:
> 
>> Not long after the start of multi-clients test, not a single station 
>> is
>> an eligible candidate for transmission since global virtual time(g_vt) 
>> is
>> smaller than the virtual airtime(s_vt) of all the stations. As a 
>> result,
>> the Tx has been blocked and throughput is quite low.
>> 
>> This may mainly due to sync mechanism and accumulative deviation from 
>> the
>> devision calculation of g_vt.
>> 
>> For example:
>> Suppose we have 50 clients in first round.
>> Round 1:
>> STA	weight	Tx_time_round  wt_sum	s_vt	g_vt  valid_for_next_Tx
>> .	.	.			.		.
>> .	.	.			.		.
>> .	.	.			.		.
>> 
>> After this round, all the stations are not valid for next transmission 
>> due
>> to accumulative deviation.
>> 
>> And if we add a new #51,
>> Round 2:
>> STA	weight	Tx_time_round	wt_sum  s_vt	g_vt  valid_for_next_Tx
>> .	.	.			.		.
>> .	.	.			.		.
>> .	.	.			.		.
>> 
>> Sync is done by:
>> max(g_vt of last round - grace period, s_vt)
>> and s_vt of #51 = max(2000 - 500, 0) + 1024 = 2524, and it is more 
>> than the
>> final g_vt of this round.
>> 
>> After this round, no more station is valid for transmission.
> 
> I'm not sure I understand this. Was there supposed to be numbers in
> those tables above?
Yes, it looks like there are some display issues. Will fix it in next 
version.
> 
> -Toke

-- 
Yibo