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From: Alexander Lobakin <aleksander.lobakin@intel.com>
To: Alexander H Duyck <alexander.duyck@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Maciej Fijalkowski <maciej.fijalkowski@intel.com>,
	Magnus Karlsson <magnus.karlsson@intel.com>,
	Michal Kubiak <michal.kubiak@intel.com>,
	Larysa Zaremba <larysa.zaremba@intel.com>,
	"Jesper Dangaard Brouer" <hawk@kernel.org>,
	Ilias Apalodimas <ilias.apalodimas@linaro.org>,
	Christoph Hellwig <hch@lst.de>,
	Paul Menzel <pmenzel@molgen.mpg.de>, <netdev@vger.kernel.org>,
	<intel-wired-lan@lists.osuosl.org>,
	<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH net-next v2 02/12] iavf: kill "legacy-rx" for good
Date: Tue, 30 May 2023 18:22:07 +0200	[thread overview]
Message-ID: <b169b20e-f782-6723-9697-215258d6f3a3@intel.com> (raw)
In-Reply-To: <09254e7cd6fd20f899f8a4ad3fbaabf223802503.camel@gmail.com>

From: Alexander H Duyck <alexander.duyck@gmail.com>
Date: Tue, 30 May 2023 08:29:10 -0700

> On Thu, 2023-05-25 at 14:57 +0200, Alexander Lobakin wrote:
>> Ever since build_skb() became stable, the old way with allocating an skb
>> for storing the headers separately, which will be then copied manually,
>> was slower, less flexible and thus obsolete.

[...]

> The "legacy-rx" was never about performance. It was mostly about
> providing a fall back in the event of an unexpected behavior. Keep in
> mind that in order to enable this we are leaving the page mapped and
> syncing it multiple times. In order to enable support for this we had
> to add several new items that I had deemed to be a bit risky such as
> support for DMA pages that were synced by the driver instead of on
> map/unmap and the use of the build_skb logic.

And now pretty much every driver doesn't do map/unmap each time and
keeps its mapping for a very long time. And now Chris noticed that and
says it's not supposed to be used like that :D

> 
> My main concern was that if we ever ran into  header corruption we
> could switch this on and then the pages would only be writable by the
> device.

[...]

> Since it has been about 6 years without any issues I would say we are
> safe to remove it.
> 
> Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>

Thanks!
Olek

WARNING: multiple messages have this Message-ID (diff)
From: Alexander Lobakin <aleksander.lobakin@intel.com>
To: Alexander H Duyck <alexander.duyck@gmail.com>
Cc: Paul Menzel <pmenzel@molgen.mpg.de>,
	Jesper Dangaard Brouer <hawk@kernel.org>,
	Larysa Zaremba <larysa.zaremba@intel.com>,
	netdev@vger.kernel.org,
	Ilias Apalodimas <ilias.apalodimas@linaro.org>,
	linux-kernel@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
	Eric Dumazet <edumazet@google.com>,
	Michal Kubiak <michal.kubiak@intel.com>,
	intel-wired-lan@lists.osuosl.org,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	"David S. Miller" <davem@davemloft.net>,
	Magnus Karlsson <magnus.karlsson@intel.com>
Subject: Re: [Intel-wired-lan] [PATCH net-next v2 02/12] iavf: kill "legacy-rx" for good
Date: Tue, 30 May 2023 18:22:07 +0200	[thread overview]
Message-ID: <b169b20e-f782-6723-9697-215258d6f3a3@intel.com> (raw)
In-Reply-To: <09254e7cd6fd20f899f8a4ad3fbaabf223802503.camel@gmail.com>

From: Alexander H Duyck <alexander.duyck@gmail.com>
Date: Tue, 30 May 2023 08:29:10 -0700

> On Thu, 2023-05-25 at 14:57 +0200, Alexander Lobakin wrote:
>> Ever since build_skb() became stable, the old way with allocating an skb
>> for storing the headers separately, which will be then copied manually,
>> was slower, less flexible and thus obsolete.

[...]

> The "legacy-rx" was never about performance. It was mostly about
> providing a fall back in the event of an unexpected behavior. Keep in
> mind that in order to enable this we are leaving the page mapped and
> syncing it multiple times. In order to enable support for this we had
> to add several new items that I had deemed to be a bit risky such as
> support for DMA pages that were synced by the driver instead of on
> map/unmap and the use of the build_skb logic.

And now pretty much every driver doesn't do map/unmap each time and
keeps its mapping for a very long time. And now Chris noticed that and
says it's not supposed to be used like that :D

> 
> My main concern was that if we ever ran into  header corruption we
> could switch this on and then the pages would only be writable by the
> device.

[...]

> Since it has been about 6 years without any issues I would say we are
> safe to remove it.
> 
> Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>

Thanks!
Olek
_______________________________________________
Intel-wired-lan mailing list
Intel-wired-lan@osuosl.org
https://lists.osuosl.org/mailman/listinfo/intel-wired-lan

  reply	other threads:[~2023-05-30 16:23 UTC|newest]

Thread overview: 59+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-05-25 12:57 [Intel-wired-lan] [PATCH net-next v2 00/12] net: intel: start The Great Code Dedup + Page Pool for iavf Alexander Lobakin
2023-05-25 12:57 ` Alexander Lobakin
2023-05-25 12:57 ` [Intel-wired-lan] [PATCH net-next v2 01/12] net: intel: introduce Intel Ethernet common library Alexander Lobakin
2023-05-25 12:57   ` Alexander Lobakin
2023-05-25 12:57 ` [Intel-wired-lan] [PATCH net-next v2 02/12] iavf: kill "legacy-rx" for good Alexander Lobakin
2023-05-25 12:57   ` Alexander Lobakin
2023-05-30 15:29   ` Alexander H Duyck
2023-05-30 15:29     ` [Intel-wired-lan] " Alexander H Duyck
2023-05-30 16:22     ` Alexander Lobakin [this message]
2023-05-30 16:22       ` Alexander Lobakin
2023-05-25 12:57 ` [Intel-wired-lan] [PATCH net-next v2 03/12] iavf: optimize Rx buffer allocation a bunch Alexander Lobakin
2023-05-25 12:57   ` Alexander Lobakin
2023-05-30 16:18   ` Alexander H Duyck
2023-05-30 16:18     ` [Intel-wired-lan] " Alexander H Duyck
2023-05-31 11:14     ` Maciej Fijalkowski
2023-05-31 11:14       ` [Intel-wired-lan] " Maciej Fijalkowski
2023-05-31 15:22       ` Alexander Lobakin
2023-05-31 15:22         ` [Intel-wired-lan] " Alexander Lobakin
2023-05-31 15:13     ` Alexander Lobakin
2023-05-31 15:13       ` Alexander Lobakin
2023-05-31 17:22       ` Alexander Duyck
2023-06-02 13:58         ` Alexander Lobakin
2023-06-02 13:58           ` Alexander Lobakin
2023-06-02 15:04           ` Alexander Duyck
2023-06-02 15:04             ` Alexander Duyck
2023-06-02 16:15             ` Alexander Lobakin
2023-06-02 16:15               ` Alexander Lobakin
2023-06-02 17:50               ` Alexander Duyck
2023-06-02 17:50                 ` Alexander Duyck
2023-06-06 12:47                 ` Alexander Lobakin
2023-06-06 12:47                   ` Alexander Lobakin
2023-06-06 14:24                   ` Alexander Duyck
2023-06-06 14:24                     ` Alexander Duyck
2023-05-25 12:57 ` [Intel-wired-lan] [PATCH net-next v2 04/12] iavf: remove page splitting/recycling Alexander Lobakin
2023-05-25 12:57   ` Alexander Lobakin
2023-05-25 12:57 ` [Intel-wired-lan] [PATCH net-next v2 05/12] iavf: always use a full order-0 page Alexander Lobakin
2023-05-25 12:57   ` Alexander Lobakin
2023-05-26  8:57   ` David Laight
2023-05-26  8:57     ` [Intel-wired-lan] " David Laight
2023-05-26 12:52     ` Alexander Lobakin
2023-05-26 12:52       ` [Intel-wired-lan] " Alexander Lobakin
2023-05-25 12:57 ` [Intel-wired-lan] [PATCH net-next v2 06/12] net: skbuff: don't include <net/page_pool.h> into <linux/skbuff.h> Alexander Lobakin
2023-05-25 12:57   ` Alexander Lobakin
2023-05-27  3:54   ` Jakub Kicinski
2023-05-27  3:54     ` [Intel-wired-lan] " Jakub Kicinski
2023-05-30 13:12     ` Alexander Lobakin
2023-05-30 13:12       ` [Intel-wired-lan] " Alexander Lobakin
2023-05-25 12:57 ` [Intel-wired-lan] [PATCH net-next v2 07/12] net: page_pool: avoid calling no-op externals when possible Alexander Lobakin
2023-05-25 12:57   ` Alexander Lobakin
2023-05-25 12:57 ` [Intel-wired-lan] [PATCH net-next v2 08/12] net: page_pool: add DMA-sync-for-CPU inline helpers Alexander Lobakin
2023-05-25 12:57   ` Alexander Lobakin
2023-05-25 12:57 ` [Intel-wired-lan] [PATCH net-next v2 09/12] iavf: switch to Page Pool Alexander Lobakin
2023-05-25 12:57   ` Alexander Lobakin
2023-05-25 12:57 ` [Intel-wired-lan] [PATCH net-next v2 10/12] libie: add common queue stats Alexander Lobakin
2023-05-25 12:57   ` Alexander Lobakin
2023-05-25 12:57 ` [Intel-wired-lan] [PATCH net-next v2 11/12] libie: add per-queue Page Pool stats Alexander Lobakin
2023-05-25 12:57   ` Alexander Lobakin
2023-05-25 12:57 ` [Intel-wired-lan] [PATCH net-next v2 12/12] iavf: switch queue stats to libie Alexander Lobakin
2023-05-25 12:57   ` Alexander Lobakin

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