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From: Alexander Lobakin <alobakin@dlink.ru>
To: Nicholas Johnson <nicholas.johnson-opensource@outlook.com.au>
Cc: David Miller <davem@davemloft.net>,
	ecree@solarflare.com, jiri@mellanox.com, edumazet@google.com,
	idosch@mellanox.com, pabeni@redhat.com, petrm@mellanox.com,
	sd@queasysnail.net, f.fainelli@gmail.com,
	jaswinder.singh@linaro.org, ilias.apalodimas@linaro.org,
	linux-kernel@vger.kernel.org, johannes.berg@intel.com,
	emmanuel.grumbach@intel.com, luciano.coelho@intel.com,
	linuxwifi@intel.com, kvalo@codeaurora.org,
	netdev@vger.kernel.org, linux-wireless@vger.kernel.org
Subject: Re: [PATCH v2 net-next] net: core: use listified Rx for GRO_NORMAL in napi_gro_receive()
Date: Mon, 25 Nov 2019 11:25:50 +0300	[thread overview]
Message-ID: <746f768684f266e5a5db1faf8314cd77@dlink.ru> (raw)
In-Reply-To: <c762f5eee08a8f2d0d6cb927d7fa3848@dlink.ru>

Alexander Lobakin wrote 25.11.2019 10:54:
> Nicholas Johnson wrote 25.11.2019 10:29:
>> Hi,
>> 
>> On Wed, Oct 16, 2019 at 10:31:31AM +0300, Alexander Lobakin wrote:
>>> David Miller wrote 16.10.2019 04:16:
>>> > From: Alexander Lobakin <alobakin@dlink.ru>
>>> > Date: Mon, 14 Oct 2019 11:00:33 +0300
>>> >
>>> > > Commit 323ebb61e32b4 ("net: use listified RX for handling GRO_NORMAL
>>> > > skbs") made use of listified skb processing for the users of
>>> > > napi_gro_frags().
>>> > > The same technique can be used in a way more common napi_gro_receive()
>>> > > to speed up non-merged (GRO_NORMAL) skbs for a wide range of drivers
>>> > > including gro_cells and mac80211 users.
>>> > > This slightly changes the return value in cases where skb is being
>>> > > dropped by the core stack, but it seems to have no impact on related
>>> > > drivers' functionality.
>>> > > gro_normal_batch is left untouched as it's very individual for every
>>> > > single system configuration and might be tuned in manual order to
>>> > > achieve an optimal performance.
>>> > >
>>> > > Signed-off-by: Alexander Lobakin <alobakin@dlink.ru>
>>> > > Acked-by: Edward Cree <ecree@solarflare.com>
>>> >
>>> > Applied, thank you.
>>> 
>>> David, Edward, Eric, Ilias,
>>> thank you for your time.
>>> 
>>> Regards,
>>> ᚷ ᛖ ᚢ ᚦ ᚠ ᚱ
>> 
>> I am very sorry to be the bearer of bad news. It appears that this
>> commit is causing a regression in Linux 5.4.0-rc8-next-20191122,
>> preventing me from connecting to Wi-Fi networks. I have a Dell XPS 
>> 9370
>> (Intel Core i7-8650U) with Intel Wireless 8265 [8086:24fd].
> 
> Hi!
> 
> It's a bit strange as this commit doesn't directly affect the packet
> flow. I don't have any iwlwifi hardware at the moment, so let's see if
> anyone else will be able to reproduce this (for now, it is the first
> report in a ~6 weeks after applying to net-next).
> Anyway, I'll investigate iwlwifi's Rx processing -- maybe I could find
> something driver-specific that might produce this.
> 
> Thank you for the report.
> 
>> I did a bisect, and this commit was named the culprit. I then applied
>> the reverse patch on another clone of Linux next-20191122, and it
>> started working.
>> 
>> 6570bc79c0dfff0f228b7afd2de720fb4e84d61d
>> net: core: use listified Rx for GRO_NORMAL in napi_gro_receive()
>> 
>> You can see more at the bug report I filed at [0].
>> 
>> [0]
>> https://bugzilla.kernel.org/show_bug.cgi?id=205647
>> 
>> I called on others at [0] to try to reproduce this - you should not 
>> pull
>> a patch because of a single reporter - as I could be wrong.
>> 
>> Please let me know if you want me to give more debugging information 
>> or
>> test any potential fixes. I am happy to help to fix this. :)

And you can also set /proc/sys/net/core/gro_normal_batch to the value
of 1 and see if there are any changes. This value makes GRO stack to
behave just like without the patch.

>> Kind regards,
>> Nicholas Johnson
> 
> Regards,
> ᚷ ᛖ ᚢ ᚦ ᚠ ᚱ

Regards,
ᚷ ᛖ ᚢ ᚦ ᚠ ᚱ

  reply	other threads:[~2019-11-25  8:26 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-14  8:00 [PATCH v2 net-next] net: core: use listified Rx for GRO_NORMAL in napi_gro_receive() Alexander Lobakin
2019-10-16  1:16 ` David Miller
2019-10-16  7:31   ` Alexander Lobakin
2019-11-25  7:29     ` Nicholas Johnson
2019-11-25  7:54       ` Alexander Lobakin
2019-11-25  8:25         ` Alexander Lobakin [this message]
2019-11-25  9:09           ` Nicholas Johnson
2019-11-25 10:31             ` Edward Cree
2019-11-25 10:58               ` Alexander Lobakin
2019-11-25 11:05                 ` Johannes Berg
2019-11-25 11:42                   ` Paolo Abeni
2019-11-25 12:02                     ` Alexander Lobakin
2019-11-25 13:21                       ` Edward Cree
2019-11-25 13:39                         ` Alexander Lobakin
2019-11-26 23:57                       ` David Miller
2019-11-27  7:47                         ` Alexander Lobakin
2019-11-27  8:30                           ` Johannes Berg
2019-11-27  9:47                         ` Alexander Lobakin
2019-11-25 12:11                     ` Kalle Valo
2019-11-25 13:07                     ` Nicholas Johnson
2019-11-25 13:11               ` Nicholas Johnson
2020-06-24 21:06 ` Jason A. Donenfeld
2020-06-24 21:28   ` Jason A. Donenfeld
2020-06-25 14:25   ` Edward Cree

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