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  • BrainwreckedTech 2:02 am on May 31, 2012 Permalink | Reply
    Tags: , atheros, atl1c, c665d-s5518, ethernet, , ifcfg, laptop, , netcfg, , networkmanager, , realtek, rtl8192ce, satellite, , toshiba, , wireless   

    Linux And Flaky ATL1C Support 

    Linux Logo Here’s something I thought I’d never see — the day that wired networking in Linux could ever be considered anything less than “it just works.”

    I recently purchased a laptop (Toshiba Satellite C655D-S5518 to be precise) and had trouble out of the gate after installing Arch Linux.  The computer would seem to hang whenever the network was involved.  (E.g., running netcfg, networkmanager, or the ip command.)  I assumed that it was wireless support that was causing the headaches, so I ran hwinfo --netcard | grep "Modules\|File" to find the kernel modules related to my networking devices.

    Device Modules: "atl1c"
    Device File: eth0
    Driver Modules: "rtl8192ce"
    Device File: wlan0

    I blacklisted rtl8192ce but that didn’t solve my problem.  (More …)

    • Jesse Robinson 5:18 am on June 14, 2012 Permalink | Reply

      I had exactly the same problem with atl1c it caused the console to freeze when the cable was unpluged,do you know the maintainer of this driver,so we can file a bug report,the problem is worse with a 3.4 kernel.
      Linux Jesse 3.4.0 #2 SMP Wed May 30 09:01:55 EST 2012 x86_64 GNU/Linux

      I really need to upgrade my kernel before submitting a bug,but scanning round it seems the bug is still there as of current kernel release.

      • BrainwreckedTech 9:55 am on June 14, 2012 Permalink | Reply

        Unfortunately I do not. Which also means I do not know how much work is going into the driver. If there’s a dedicated team, then they just need time. If it’s a single person, he could probably use some help even it’s nothing more than yet another environment in which to see how the driver code behaves. Just be prepared that this might entail setting up a debug environment (e.g. compiling and using a kernel that spits out debug symbols, etc.). If you can code, all the better. 🙂

        Either way, as the driver is listed as EXPERIMENTAL, it’ll do no good to file normal bug reports as the people behind this driver already know that it is not 100%.

    • GreyGeek 8:47 am on August 12, 2013 Permalink | Reply

      As of Aug 12, 2013 this atl1c bug is affecting my Acer V3-771G laptop running Kubuntu 12.04.2 with all updates. On my system it shows up as a random disconnect and reconnect. Most of the time the reconnect is almost immediately, but sometimes it may take as much as 30 seconds. I switched from NetworkManager to WICD and the problem remains, but perhaps not as frequent. From once every 5 minutes to once every 10 minutes. There is NO messages indicating the disconnect & reconnect in any system log.
      I am using the 3.8.0-27-generic kernel.

  • BrainwreckedTech 3:24 am on May 20, 2009 Permalink | Reply
    Tags: ethernet, gigabit ethernet, , , , , ,   

    HOWTO: Optimize Gigabit Networking in Linux 

    Ethernet Cable FullLinux Logo Half Even if you have a gigabit networking adapter and a gigabit switch capable of jumbo frames, Linux still uses the default MTU size of 1500. To get something better, you need to configure things by hand.

    The reason for this is that the IETF has never standardized anything above 1500. You might very well have gigabit ethernet equipment that either does not have jumbo frame support, or may be very disappointed to find out that “jumbo frame” can be used to describe any packet size between 1500 and 9000.

    To make matters worse, not every gigabit ethernet switch handles mixed networking the same. You would think a gigabit switch would guarantee a 1gb connection between two computers with 1gb networking adapters, but under various circumstances, this isn’t always the case. Optimally, it would be best to separate your 100mb and 1gb devices onto two different switches, but this isn’t guaranteed to work.

    Now that we have all the caveats out of the way, read on if you want to start optimizing.

    (More …)

    • strange 4:52 pm on June 11, 2009 Permalink | Reply

      why do the MTU’s have to match? a workstation accessing the internet will have several devices between it and the internet, a linksys router running linux being a common one, and it will be a much lower MTU.

      the lowest common denominator will be all the gear out at the boundaries, which all the machines and servers will likely have to talk to at some point. so what do you do then?

      • brainwreckedtech 11:11 pm on June 12, 2009 Permalink | Reply

        The MTUs don’t have to match unless you enjoy having your LAN speed crippled as your computers break apart packets on their own trying to reach a common denominator. While the advice here is for optimizing the speed that computers communicate on a LAN, not the Internet, keep in mind that computers with bigger MTUs will have no trouble accepting smaller packets from computers with smaller MTUs. Your Internet download speeds won’t be affected, but your upload speeds might. However, most people’s Internet connection speed (in the US, at least) doesn’t even hit 1mb/s upstream. Factor that measly speed with all the latency due to routing, server capacity, etc., and the upload speed degradation from mismatched MTUs with the Internet becomes the least of your problems.

        By no means should you adjust the MTU of a machine on your LAN if its sole purpose to upload data to the billions of anonymous users on the net. At the same time, you should consider getting that machine off your private network in the event a security breach. A simple double-NAT will do.

    • BlueSherpa 2:17 pm on February 7, 2010 Permalink | Reply


      The “theoretical” limit of gigabit, also known as the wire speed, is 125MB/s (wikipedia, 2010).

      “one can only get a little over one-third of the theoretical limit of gigabit” is not true. 900Mb/s can be attained at the normal 1500 byte MTU setting (Schluting, 2007).

      Wikipedia http://en.wikipedia.org/wiki/Gigabit_Ethernet

      Schulting http://www.enterprisenetworkingplanet.com/nethub/article.php/3485486

      • brainwreckedtech 4:33 pm on February 8, 2010 Permalink | Reply

        125mB/s (m being read the decimal “mega” of 1000) was never in dispute, but I did botch my original 101MB/s (M being read as the computer “mega” of 1024). The correct calculation is 1,000,000,000 bits ÷ 8 bits/byte ÷ 1024 bytes/kilobyte ÷ 1024 kilobytes/megabyte = 119.21MB/s.

        I’ll recant my “never,” but Schulting used server-class hardware and mem-to-mem copying. Consumers are going to be hard-pressed to find such equipment and are more apt re-use old equipment and go by drive-to-drive copying over Ethernet. Following his advice gave my speed a bump to an average of 43MB/s with the range anywhere from 36MB/s to 50MB/s. Nice, but far short of 119 MB/s.

        • august 8:39 pm on February 10, 2010 Permalink | Reply

          In networking, “mega” was always the proper “mega” – 1000000.

          The only thing that really ever used the 2^10 thing was memory sizes, because they naturally come in powers of 2.
          (And please use the proper prefixes (MiB etc) if you’re going to use the binary variant.)

          So 125MB/s is the right number.

          Also, if you’re doing drive-to-drive copying, you’re probably measuring the speed of your disk, and not the ethernet.

          • brainwreckedtech 4:37 am on February 11, 2010 Permalink | Reply

            Now you’re just picking nits.

            210 is used for all storage sizes, not just memory.

            125mB/s is a correct number. So is 119MB/s when that number is the theoretical ceiling that will be reported by any OS transferring a file.

            I’ve seen MiB, and guess what? Fuck it. Using M for 220 and Mi for million is great, but what do you do for the giga level? Do they use G for 230 and Tr for trillion? NO, THEY USE Gi FOR TRILLION. And you can’t go back and say Gi = decimal giga because, if that was their intent, they should have used Me for decimal mega. So you can try and use that system if you want. I see no harm in using caps for bigger values and lowercase for smaller values because — at least to me — it makes sense and can be made consistent.

            Finally, where do you think the data is coming from that’s being served over Ethernet? The config I’m using is two 250GB Samsung SP2504C drives in software RAID 0 in a file server. These drives have been rated for an average random reads and writes around 45MB/s. RAID 0 absolutely can double the average speed of random reads and writes, so that gives me a ceiling of 90MB/s. There is negligible, if any, difference between Linux software RAID and hardware RAID. I was only getting 50MB/s tops, so it wasn’t the hard drives. The NICs are on-board, so it isn’t the PCI bus. And even if it was, it was still below the 78MB/s limit of 33MHz PCI.

            • ah 6:35 am on March 12, 2014 Permalink | Reply

              when I test, I dont copy data from and to actual disk drives, I use dd to copy /dev/zero over the network to /dev/null at the other end, which cuts out the disk drive completely. Do you not use this method?

              • BrainwreckedTech 4:02 am on March 19, 2014 Permalink | Reply

                Not a bad idea, but shortcuts (large stream of only 0’s) can be taken at the kernel level. Better to take an ISO (or file created with /dev/urandom) inside a tmpfs and copy that.

    • Darr247 12:02 pm on December 16, 2010 Permalink | Reply

      You’ve got it backwards, so no wonder you think it’s a bad idea. 😉

      M=10^6; Mi=2^20

      The idea is, hard drive manufacturers used (some would argue “correctly”) the SI version of mega (ergo influenced what peoples’ idea of MB should be on computers) to mean 1,000,000 bytes, so back at the turn of the century the IEC designated MiB to mean 1,048,576 bytes.

      It’s pronounced mebibytes, short for mega binary bytes.

      G = 10^9; Gi = 2^30 (giga/giba)
      T = 10^12; Ti = 2^40 (tera/tebi)
      et cetera (P/Pi, E/Ei, Z/Zi) up to
      Y = 10^24; Yi = 2^80 (yotta/yobi)

      I don’t know that SI has abbreviations for values greater than 10^24… but when we get to 10^100 capacities, hard drive manufacturers will no doubt start using “googlebytes” thanks to the non-math guy who originally registered the domain name (instead of “googol” which is what the search engine’s inventors intended).

      Implicitly, b=bits and B=bytes, also.

      I’ve never seen anyone use G or Gi for trillion. Got a cite?

      Finally, thanks for the linux gigabit tuning tips.

    • BrainwreckedTech 6:07 am on December 26, 2010 Permalink | Reply

      You’re right about me being backwards on X and Xi.

      The hard drive manufacturers started using the decimal interpretation because it meant they could advertise bigger numbers. (Never attribute to malice what can be adequately explained by stupidity…or greed.) No one paid much mind back in the days of the kilobyte because the difference was small, and we’re used to a bit of fibbing from marketing departments. The excuse, “you lose some space due to formatting,” held enough truth to keep most users calm. I can’t recall exactly when the difference became a major ordeal, but fuzzy hindsight says it probably came with the introduction of the first gigabyte drives — kinda hard to chalk the drop from 1GB to 953MB to formatting.

      Tangent: Networking came after hard drives. They took a page from hard drive manufacturer’s play book and took it a step further by never graduating beyond bits.

      You can see Gi in use in Gnome and KDE. Besides, by definition, it is one trillion. 1,000,000,000 or 1,073,741,824 depending on which definition.

    • Pyrrhic 1:26 pm on February 23, 2011 Permalink | Reply

      Thank you for posting this I had a SIOC… etc error, your post allowed me to fix this. The MTU discussion is also very, very useful. Again…thanks!



    • Markus Torstensson 6:19 am on June 23, 2011 Permalink | Reply

      Thanks dude 😀 Works like a charm. Kinda shame about the prefix-flamewar you had to put up with.

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