From: Christian Lamparter <chunkeey@googlemail.com>
To: Ben Greear <greearb@candelatech.com>
Cc: "linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>
Subject: Re: Why is throughput so bad with lots of virtual stations?
Date: Sat, 31 Mar 2012 11:59:54 +0200 [thread overview]
Message-ID: <201203311159.55238.chunkeey@googlemail.com> (raw)
In-Reply-To: <4F76806E.2010101@candelatech.com>
On Saturday 31 March 2012 05:56:30 Ben Greear wrote:
> I notice that when I get, say, 200 virtual stations on a radio (ath9k),
> the total throughput becomes about 100 packets per second. It can run
> several thousands of packets per second with 10 or so stations.
is this tcp or udp "throughput"?
Anyway, I don't know much about your AP. But If it's mac80211 based
then you might also run into a problem with ath9k vs mac80211 for
every sta_info_get_bss [used by ieee80211_find_sta et. al] call.
You see, the station hash table uses the last byte of a station's
MAC as the "HASH" [see STA_HASH]. So for 00:11:22:33:44:55, the hash
is "55". Now, ath9k uses a mac mask for it's VIFs as well, only it
starts from the other direction [i.e.:] xy:11:22:33:44:55.
[e.g.: vif1: 00:11:22:33:44:55, vif2: 04:11:22:33:44:55,
vif3: 0c:11:22:33:44:55, ...]
So, mac80211's sta hash table really becomes a "long list". Which has
to be traversed by the driver and stack several times.
> According to the xmit debugfs file, the radio is basically idle.
> It's queues are empty almost all of the time, few retransmits, etc.
>
> This is on the 3.0.26 kernel.
>
> If anyone has any ideas of what might need work, please let me know.
>
> I'll start digging into the code to see what I can see.
Regards,
Chr
next prev parent reply other threads:[~2012-03-31 10:00 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-31 3:56 Why is throughput so bad with lots of virtual stations? Ben Greear
2012-03-31 9:59 ` Christian Lamparter [this message]
2012-03-31 20:39 ` Ben Greear
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=201203311159.55238.chunkeey@googlemail.com \
--to=chunkeey@googlemail.com \
--cc=greearb@candelatech.com \
--cc=linux-wireless@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).