Date:   Sat, 9 Feb 2019 12:03:00 +0100
From:   Stanislaw Gruszka <sgruszka@redhat.com>
To:     Tom Psyborg <pozega.tomislav@gmail.com>
Cc:     linux-wireless@vger.kernel.org,
        Randy Oostdyk <linux-kernel@oostdyk.com>,
        Daniel Golle <daniel@makrotopia.org>,
        Felix Fietkau <nbd@nbd.name>, Mathias Kresin <dev@kresin.me>
Subject: Re: [PATCH v2 3/3] rt2x00: do not print error when queue is full
Message-ID: <20190209110259.GA14900@redhat.com>
References: <1545318971-28351-1-git-send-email-sgruszka@redhat.com>
 <1545318971-28351-3-git-send-email-sgruszka@redhat.com>
 <CAKR_QVJeteexpQX=pJm17WrrarmihYw56hKuTbsNagbcA6U96A@mail.gmail.com>
 <20181221095938.GA29536@redhat.com>
 <CAKR_QVKQMcGGpY_3ur9kFjuYpaKgca=YfUJxjSjLEfP1HELuJw@mail.gmail.com>
 <20181227102535.GA25885@redhat.com>
 <CAKR_QVK_2j6a9YiwUEKuWF+ss0-pr808Sr=AUrX4a6L3Zw=F0w@mail.gmail.com>
 <20190102081934.GA5300@redhat.com>
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On Wed, Jan 02, 2019 at 09:19:34AM +0100, Stanislaw Gruszka wrote:
> On Fri, Dec 28, 2018 at 01:45:27AM +0100, Tom Psyborg wrote:
> > >
> > > I move prints to debug level for for "arrived at non-free entry" from
> > > "Dropping frame due to full tx queue" . For some users those 5 patches
> > > improve things, they fix problem of router connection hung completely.
> > > Printk problem is connection stall due to CPU being busy, but
> > > is possible to reconnect to AP after that. It's different issue.
> > >
> > yes they fix hung. same hung that does this single patch fix by moving
> > to dbg so they're not printed at all. FYI "Dropping frame due to full
> > tx queue" causes "arrived at non-free entry" eventually that freezes
> > interface so only reboot helps, removing "Dropping frame due to full
> > tx queue" from printing to logs prevents this kind of hung and is
> > better solution than 5 patches.
> 
> I wonder why are you confident about this ? And also why 5 patches
> fixed the hung if there were still "Dropping frame ..." prints ?
> 
> Anyway I'll ask people on the bz for confirmation, if stop printing
> is sufficient to fix the wifi hung.
> 
> > oh and don't forget to add note that
> > rt2x00_err/rt2x00_dbg prints can cause serious bug so you don't
> > acidentally enable them again in a year or two!
> 
> I think I will remember that, for others git changelog should
> be sufficient.
>  
> > > Also 'result in lower throughput' is over-generalized statement. More
> > > precise would be 'it lower throughput on some test cases', but even
> > > in those specific cases, throughput vary randomly with and without
> > > patches.
> > >
> > 
> > 100Mbps TX 70Mbps RX without and 80Mbps TX 55 Mbps RX with 5
> > patches--> EA2750 HT40 CH2 4.14.82+4.19-rc5-1-1
> 
> Ok, this is different case that you presented before on USB devices.
> And I'm more concerned about it, because changes with MMIO ware
> much bigger (for USB only some code was moved and some flush
> changed were done). Please check attached patch, if it fixes
> throughput regression for you ?

So what is the point complaining that I do not provide patches for
testing and when I do, ignore that ?

Anyway I have now MT7620A device and was capable to reproduce the
performance regression. Will provide patches to fix it and still
prevent tx queues hungs.

Stanislaw