From: Michal Kazior <michal.kazior@tieto.com>
To: Dave Taht <dave.taht@gmail.com>
Cc: "Felix Fietkau" <nbd@nbd.name>,
make-wifi-fast@lists.bufferbloat.net,
linux-wireless <linux-wireless@vger.kernel.org>,
"Toke Høiland-Jørgensen" <toke@toke.dk>
Subject: Re: [Make-wifi-fast] TCP performance regression in mac80211 triggered by the fq code
Date: Tue, 19 Jul 2016 15:10:48 +0200 [thread overview]
Message-ID: <CA+BoTQnb4ynzSFs-2btkg-uqXUmfZwMa76DhRL6weu9H48rCAA@mail.gmail.com> (raw)
In-Reply-To: <CAA93jw4GQknawtp6Lo3ZM8=qW=p2eTnZ_krC7AvnNbKwp8R5SQ@mail.gmail.com>
On 12 July 2016 at 16:02, Dave Taht <dave.taht@gmail.com> wrote:
[...]
>>> tcp_limit_output_bytes is?
>> 262144
>
> I keep hoping to be able to reduce this to something saner like 4096
> one day. It got bumped to 64k based on bad wifi performance once, and
> then to it's current size to make the Xen folk happier.
Not sure if it's possible. You do need this to be at least as big as a
single A-MPDU can get. In extreme 11ac cases it can be pretty big.
I recall a discussion from a long time ago and the tcp limit output
logic was/is coupled with the assumption that tx-completions always
come max 1ms after tx submission. This is rather tricky to *guarantee*
on wifi, especially with firmware blobs, big aggregates, lots of
stations and retries.
Michał
next prev parent reply other threads:[~2016-07-19 13:10 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <11fa6d16-21e2-2169-8d18-940f6dc11dca@nbd.name>
2016-07-12 12:13 ` Dave Taht
2016-07-12 13:21 ` Felix Fietkau
2016-07-12 14:02 ` Dave Taht
2016-07-13 7:57 ` Dave Taht
2016-07-13 8:53 ` Felix Fietkau
2016-07-13 9:13 ` Dave Taht
2016-07-19 13:10 ` Michal Kazior [this message]
[not found] ` <87shvfujl4.fsf@toke.dk>
[not found] ` <CAA93jw6z53P+JCPsjYD-vaY+9vq9ZO-Ob_cXm0AE76uVcM=F9g@mail.gmail.com>
[not found] ` <87bn23ui87.fsf@toke.dk>
2016-07-12 13:03 ` Dave Taht
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