From: Russell King - ARM Linux <linux@armlinux.org.uk> To: Eric Nelson <eric@nelint.com> Cc: Eric Dumazet <edumazet@google.com>, "linux-arm-kernel@lists.infradead.org" <linux-arm-kernel@lists.infradead.org>, "netdev@vger.kernel.org" <netdev@vger.kernel.org>, Fugang Duan <fugang.duan@nxp.com>, Troy Kisky <troy.kisky@boundarydevices.com>, Otavio Salvador <otavio@ossystems.com.br>, Simone <cjb.sw.nospam@gmail.com> Subject: Re: Alignment issues with freescale FEC driver Date: Fri, 23 Sep 2016 19:37:25 +0100 [thread overview] Message-ID: <20160923183725.GC1041@n2100.armlinux.org.uk> (raw) In-Reply-To: <d0d6f333-c6fc-6572-0633-d7c2c29b8b3f@nelint.com> On Fri, Sep 23, 2016 at 11:26:18AM -0700, Eric Nelson wrote: > So the question is: should we just live with this and acknowledge a > performance penalty of bad alignment or do something about it? Well, I've no interest in trying to do anything with the FEC driver anymore, as I'll just generate another big patch stack which won't make it into the kernel in a timely fashion - my last attempt at improving the FEC driver was dogged with conflicting changes and I gave up with it in the end. I ended up spending a full cycle rebasing, re-testing, and re-evaluating their performance only to find that I'd missed the merge window again, and other conflicting changes got merged which meant that I had to start from the beginning again. > I'm not sure the cost (or the details) of Eric's proposed fix of allocating > and copying the header to another skb. I had a quick look at this, and although Eric's idea may be a good idea, it doesn't contain enough details for me to be able to implement it - eg, I've no idea how to attach the 128-byte skb to the beginning of a previously allocated skb containing the rest of the packet. I've just looked through linux/skbuff.h and I can't see anything that takes two sk_buff's that would do the job. However, I don't think that's necessary in this case, because the iMX6 FEC supports the 16-bit alignment of the packet, if only it was enabled in hardware and the driver caters for it. -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.
WARNING: multiple messages have this Message-ID (diff)
From: linux@armlinux.org.uk (Russell King - ARM Linux) To: linux-arm-kernel@lists.infradead.org Subject: Alignment issues with freescale FEC driver Date: Fri, 23 Sep 2016 19:37:25 +0100 [thread overview] Message-ID: <20160923183725.GC1041@n2100.armlinux.org.uk> (raw) In-Reply-To: <d0d6f333-c6fc-6572-0633-d7c2c29b8b3f@nelint.com> On Fri, Sep 23, 2016 at 11:26:18AM -0700, Eric Nelson wrote: > So the question is: should we just live with this and acknowledge a > performance penalty of bad alignment or do something about it? Well, I've no interest in trying to do anything with the FEC driver anymore, as I'll just generate another big patch stack which won't make it into the kernel in a timely fashion - my last attempt at improving the FEC driver was dogged with conflicting changes and I gave up with it in the end. I ended up spending a full cycle rebasing, re-testing, and re-evaluating their performance only to find that I'd missed the merge window again, and other conflicting changes got merged which meant that I had to start from the beginning again. > I'm not sure the cost (or the details) of Eric's proposed fix of allocating > and copying the header to another skb. I had a quick look at this, and although Eric's idea may be a good idea, it doesn't contain enough details for me to be able to implement it - eg, I've no idea how to attach the 128-byte skb to the beginning of a previously allocated skb containing the rest of the packet. I've just looked through linux/skbuff.h and I can't see anything that takes two sk_buff's that would do the job. However, I don't think that's necessary in this case, because the iMX6 FEC supports the 16-bit alignment of the packet, if only it was enabled in hardware and the driver caters for it. -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.
next prev parent reply other threads:[~2016-09-23 18:37 UTC|newest] Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-09-23 16:43 Alignment issues with freescale FEC driver Eric Nelson 2016-09-23 16:43 ` Eric Nelson 2016-09-23 16:54 ` Eric Dumazet 2016-09-23 16:54 ` Eric Dumazet 2016-09-23 17:19 ` Eric Nelson 2016-09-23 17:19 ` Eric Nelson 2016-09-23 17:33 ` Eric Nelson 2016-09-23 17:33 ` Eric Nelson 2016-09-23 18:13 ` Andrew Lunn 2016-09-23 18:13 ` Andrew Lunn 2016-09-23 18:30 ` Russell King - ARM Linux 2016-09-23 18:30 ` Russell King - ARM Linux 2016-09-23 18:39 ` Eric Nelson 2016-09-23 18:39 ` Eric Nelson 2016-09-23 18:35 ` Eric Nelson 2016-09-23 18:35 ` Eric Nelson 2016-09-24 2:45 ` David Miller 2016-09-24 2:45 ` David Miller 2016-09-24 5:13 ` Andy Duan 2016-09-24 5:13 ` Andy Duan 2016-09-24 14:42 ` [PATCH 0/3] net: fec: updates to align IP header Eric Nelson 2016-09-24 14:42 ` [PATCH 1/3] net: fec: remove QUIRK_HAS_RACC from i.mx25 Eric Nelson 2016-09-24 14:42 ` [PATCH 2/3] net: fec: remove QUIRK_HAS_RACC from i.mx27 Eric Nelson 2016-09-24 14:42 ` [PATCH 3/3] net: fec: align IP header in hardware Eric Nelson 2016-09-26 9:26 ` David Laight 2016-09-26 18:39 ` Eric Nelson 2016-09-28 16:42 ` David Laight 2016-09-28 17:14 ` Eric Nelson 2016-09-28 17:25 ` Russell King - ARM Linux 2016-09-28 18:01 ` Eric Nelson 2016-09-29 11:07 ` David Laight 2016-09-30 13:27 ` Eric Nelson 2016-09-30 13:49 ` David Laight 2016-09-30 14:16 ` Eric Nelson 2016-10-01 19:52 ` Russell King - ARM Linux 2016-10-03 16:42 ` David Laight 2016-10-03 18:48 ` Eric Nelson 2016-10-08 2:44 ` Andy Duan 2016-09-24 15:09 ` [PATCH 0/3] net: fec: updates to align IP header Andy Duan 2016-09-24 15:29 ` Eric Nelson 2016-09-27 11:40 ` David Miller 2016-09-24 2:43 ` Alignment issues with freescale FEC driver David Miller 2016-09-24 2:43 ` David Miller 2016-09-24 12:27 ` Eric Nelson 2016-09-24 12:27 ` Eric Nelson 2016-09-23 17:37 ` Russell King - ARM Linux 2016-09-23 17:37 ` Russell King - ARM Linux 2016-09-23 18:26 ` Eric Nelson 2016-09-23 18:26 ` Eric Nelson 2016-09-23 18:37 ` Russell King - ARM Linux [this message] 2016-09-23 18:37 ` Russell King - ARM Linux 2016-09-23 18:49 ` Eric Nelson 2016-09-23 18:49 ` Eric Nelson 2016-09-23 20:22 ` Uwe Kleine-König 2016-09-23 20:22 ` Uwe Kleine-König
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=20160923183725.GC1041@n2100.armlinux.org.uk \ --to=linux@armlinux.org.uk \ --cc=cjb.sw.nospam@gmail.com \ --cc=edumazet@google.com \ --cc=eric@nelint.com \ --cc=fugang.duan@nxp.com \ --cc=linux-arm-kernel@lists.infradead.org \ --cc=netdev@vger.kernel.org \ --cc=otavio@ossystems.com.br \ --cc=troy.kisky@boundarydevices.com \ /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: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.