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  1. 27 Aug, 2011 8 commits
  3. 26 Aug, 2011 26 commits
  5. 25 Aug, 2011 6 commits
    • Francois Romieu's avatar
      sunbmac: use standard #defines from mii.h. · cd296780
      Francois Romieu authored 
      Signed-off-by: default avatarFrancois Romieu <romieu@fr.zoreil.com>
      cd296780
    • Francois Romieu's avatar
      dl2k: use standard #defines from mii.h. · 78f6a6bd
      Francois Romieu authored 
      Signed-off-by: default avatarFrancois Romieu <romieu@fr.zoreil.com>
      78f6a6bd
    • Tim Chen's avatar
      Scm: Remove unnecessary pid & credential references in Unix socket's send and receive path · 0856a304
      Tim Chen authored 
      Patch series 109f6e39..7361c36c back in 2.6.36 added functionality to
allow credentials to work across pid namespaces for packets sent via
UNIX sockets.  However, the atomic reference counts on pid and
credentials caused plenty of cache bouncing when there are numerous
threads of the same pid sharing a UNIX socket.  This patch mitigates the
problem by eliminating extraneous reference counts on pid and
credentials on both send and receive path of UNIX sockets. I found a 2x
improvement in hackbench's threaded case.

On the receive path in unix_dgram_recvmsg, currently there is an
increment of reference count on pid and credentials in scm_set_cred.
Then there are two decrement of the reference counts.  Once in scm_recv
and once when skb_free_datagram call skb->destructor function
unix_destruct_scm.  One pair of increment and decrement of ref count on
pid and credentials can be eliminated from the receive path.  Until we
destroy the skb, we already set a reference when we created the skb on
the send side.

On the send path, there are two increments of ref count on pid and
credentials, once in scm_send and once in unix_scm_to_skb.  Then there
is a decrement of the reference counts in scm_destroy's call to
scm_destroy_cred at the end of unix_dgram_sendmsg functions.   One pair
of increment and decrement of the reference counts can be removed so we
only need to increment the ref counts once.

By incorporating these changes, for hackbench running on a 4 socket
NHM-EX machine with 40 cores, the execution of hackbench on
50 groups of 20 threads sped up by factor of 2.

Hackbench command used for testing:
./hackbench 50 thread 2000
Signed-off-by: default avatarTim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      0856a304
    • Michio Honda's avatar
      sctp: Bundle HEAERTBEAT into ASCONF_ACK · 6af29ccc
      Michio Honda authored 
      With this patch a HEARTBEAT chunk is bundled into the ASCONF-ACK
for ADD IP ADDRESS, confirming the new destination as quickly as
possible.
Signed-off-by: default avatarMichio Honda <micchie@sfc.wide.ad.jp>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      6af29ccc
    • Michio Honda's avatar
      sctp: HEARTBEAT negotiation after ASCONF · f207c050
      Michio Honda authored 
      This patch fixes BUG that the ASCONF receiver transmits DATA chunks
to the newly added UNCONFIRMED destination.
Signed-off-by: default avatarMichio Honda <micchie@sfc.wide.ad.jp>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      f207c050
    • Nandita Dukkipati's avatar
      Proportional Rate Reduction for TCP. · a262f0cd
      Nandita Dukkipati authored 
      This patch implements Proportional Rate Reduction (PRR) for TCP.
PRR is an algorithm that determines TCP's sending rate in fast
recovery. PRR avoids excessive window reductions and aims for
the actual congestion window size at the end of recovery to be as
close as possible to the window determined by the congestion control
algorithm. PRR also improves accuracy of the amount of data sent
during loss recovery.

The patch implements the recommended flavor of PRR called PRR-SSRB
(Proportional rate reduction with slow start reduction bound) and
replaces the existing rate halving algorithm. PRR improves upon the
existing Linux fast recovery under a number of conditions including:
  1) burst losses where the losses implicitly reduce the amount of
outstanding data (pipe) below the ssthresh value selected by the
congestion control algorithm and,
  2) losses near the end of short flows where application runs out of
data to send.

As an example, with the existing rate halving implementation a single
loss event can cause a connection carrying short Web transactions to
go into the slow start mode after the recovery. This is because during
recovery Linux pulls the congestion window down to packets_in_flight+1
on every ACK. A short Web response often runs out of new data to send
and its pipe reduces to zero by the end of recovery when all its packets
are drained from the network. Subsequent HTTP responses using the same
connection will have to slow start to raise cwnd to ssthresh. PRR on
the other hand aims for the cwnd to be as close as possible to ssthresh
by the end of recovery.

A description of PRR and a discussion of its performance can be found at
the following links:
- IETF Draft:
    http://tools.ietf.org/html/draft-mathis-tcpm-proportional-rate-reduction-01
- IETF Slides:
    http://www.ietf.org/proceedings/80/slides/tcpm-6.pdf
    http://tools.ietf.org/agenda/81/slides/tcpm-2.pdf
- Paper to appear in Internet Measurements Conference (IMC) 2011:
    Improving TCP Loss Recovery
    Nandita Dukkipati, Matt Mathis, Yuchung Cheng
Signed-off-by: default avatarNandita Dukkipati <nanditad@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      a262f0cd
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