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  1. Dec 21, 2011
    • Gerlando Falauto's avatar
      net: have ipconfig not wait if no dev is available · cd7816d1
      Gerlando Falauto authored 
      previous commit 3fb72f1e


makes IP-Config wait for carrier on at least one network device.

Before waiting (predefined value 120s), check that at least one device
was successfully brought up. Otherwise (e.g. buggy bootloader
which does not set the MAC address) there is no point in waiting
for carrier.

Cc: Micha Nelissen <micha@neli.hopto.org>
Cc: Holger Brunck <holger.brunck@keymile.com>
Signed-off-by: default avatarGerlando Falauto <gerlando.falauto@keymile.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      cd7816d1
    • Thomas Graf's avatar
      sctp: Do not account for sizeof(struct sk_buff) in estimated rwnd · a76c0adf
      Thomas Graf authored 
      

When checking whether a DATA chunk fits into the estimated rwnd a
full sizeof(struct sk_buff) is added to the needed chunk size. This
quickly exhausts the available rwnd space and leads to packets being
sent which are much below the PMTU limit. This can lead to much worse
performance.

The reason for this behaviour was to avoid putting too much memory
pressure on the receiver. The concept is not completely irational
because a Linux receiver does in fact clone an skb for each DATA chunk
delivered. However, Linux also reserves half the available socket
buffer space for data structures therefore usage of it is already
accounted for.

When proposing to change this the last time it was noted that this
behaviour was introduced to solve a performance issue caused by rwnd
overusage in combination with small DATA chunks.

Trying to reproduce this I found that with the sk_buff overhead removed,
the performance would improve significantly unless socket buffer limits
are increased.

The following numbers have been gathered using a patched iperf
supporting SCTP over a live 1 Gbit ethernet network. The -l option
was used to limit DATA chunk sizes. The numbers listed are based on
the average of 3 test runs each. Default values have been used for
sk_(r|w)mem.

Chunk
Size    Unpatched     No Overhead
-------------------------------------
   4    15.2 Kbit [!]   12.2 Mbit [!]
   8    35.8 Kbit [!]   26.0 Mbit [!]
  16    95.5 Kbit [!]   54.4 Mbit [!]
  32   106.7 Mbit      102.3 Mbit
  64   189.2 Mbit      188.3 Mbit
 128   331.2 Mbit      334.8 Mbit
 256   537.7 Mbit      536.0 Mbit
 512   766.9 Mbit      766.6 Mbit
1024   810.1 Mbit      808.6 Mbit

Signed-off-by: default avatarThomas Graf <tgraf@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      a76c0adf
  3. Dec 20, 2011
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