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  1. 25 8月, 2011 3 次提交
    • N
      Proportional Rate Reduction for TCP. · a262f0cd
      由 Nandita Dukkipati 提交于 
      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: NNandita Dukkipati <nanditad@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      a262f0cd
    • C
      af-packet: Added TPACKET_V3 headers. · 0d4691ce
      由 chetan loke 提交于 
      Added TPACKET_V3 definitions.
Signed-off-by: NChetan Loke <loke.chetan@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      0d4691ce
    • I
      net: convert core to skb paged frag APIs · ea2ab693
      由 Ian Campbell 提交于 
      Signed-off-by: NIan Campbell <ian.campbell@citrix.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: "Michał Mirosław" <mirq-linux@rere.qmqm.pl>
Cc: netdev@vger.kernel.org
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      ea2ab693
  3. 23 8月, 2011 1 次提交
  5. 19 8月, 2011 1 次提交
  7. 18 8月, 2011 3 次提交
  9. 17 8月, 2011 5 次提交
  11. 16 8月, 2011 1 次提交
  13. 15 8月, 2011 1 次提交
  15. 13 8月, 2011 4 次提交
  17. 12 8月, 2011 1 次提交
    • V
      move RLIMIT_NPROC check from set_user() to do_execve_common() · 72fa5997
      由 Vasiliy Kulikov 提交于 
      The patch http://lkml.org/lkml/2003/7/13/226 introduced an RLIMIT_NPROC
check in set_user() to check for NPROC exceeding via setuid() and
similar functions.

Before the check there was a possibility to greatly exceed the allowed
number of processes by an unprivileged user if the program relied on
rlimit only.  But the check created new security threat: many poorly
written programs simply don't check setuid() return code and believe it
cannot fail if executed with root privileges.  So, the check is removed
in this patch because of too often privilege escalations related to
buggy programs.

The NPROC can still be enforced in the common code flow of daemons
spawning user processes.  Most of daemons do fork()+setuid()+execve().
The check introduced in execve() (1) enforces the same limit as in
setuid() and (2) doesn't create similar security issues.

Neil Brown suggested to track what specific process has exceeded the
limit by setting PF_NPROC_EXCEEDED process flag.  With the change only
this process would fail on execve(), and other processes' execve()
behaviour is not changed.

Solar Designer suggested to re-check whether NPROC limit is still
exceeded at the moment of execve().  If the process was sleeping for
days between set*uid() and execve(), and the NPROC counter step down
under the limit, the defered execve() failure because NPROC limit was
exceeded days ago would be unexpected.  If the limit is not exceeded
anymore, we clear the flag on successful calls to execve() and fork().

The flag is also cleared on successful calls to set_user() as the limit
was exceeded for the previous user, not the current one.

Similar check was introduced in -ow patches (without the process flag).

v3 - clear PF_NPROC_EXCEEDED on successful calls to set_user().
Reviewed-by: NJames Morris <jmorris@namei.org>
Signed-off-by: NVasiliy Kulikov <segoon@openwall.com>
Acked-by: NNeilBrown <neilb@suse.de>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      72fa5997
  19. 10 8月, 2011 2 次提交
  21. 09 8月, 2011 8 次提交
  23. 08 8月, 2011 2 次提交
  25. 07 8月, 2011 5 次提交
    • L
      vfs: optimize inode cache access patterns · 3ddcd056
      由 Linus Torvalds 提交于 
      The inode structure layout is largely random, and some of the vfs paths
really do care.  The path lookup in particular is already quite D$
intensive, and profiles show that accessing the 'inode->i_op->xyz'
fields is quite costly.

We already optimized the dcache to not unnecessarily load the d_op
structure for members that are often NULL using the DCACHE_OP_xyz bits
in dentry->d_flags, and this does something very similar for the inode
ops that are used during pathname lookup.

It also re-orders the fields so that the fields accessed by 'stat' are
together at the beginning of the inode structure, and roughly in the
order accessed.

The effect of this seems to be in the 1-2% range for an empty kernel
"make -j" run (which is fairly kernel-intensive, mostly in filename
lookup), so it's visible.  The numbers are fairly noisy, though, and
likely depend a lot on exact microarchitecture.  So there's more tuning
to be done.
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      3ddcd056
    • L
      vfs: renumber DCACHE_xyz flags, remove some stale ones · 830c0f0e
      由 Linus Torvalds 提交于 
      Gcc tends to generate better code with small integers, including the
DCACHE_xyz flag tests - so move the common ones to be first in the list.
Also just remove the unused DCACHE_INOTIFY_PARENT_WATCHED and
DCACHE_AUTOFS_PENDING values, their users no longer exists in the source
tree.

And add a "unlikely()" to the DCACHE_OP_COMPARE test, since we want the
common case to be a nice straight-line fall-through.
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      830c0f0e
    • D
      net: Compute protocol sequence numbers and fragment IDs using MD5. · 6e5714ea
      由 David S. Miller 提交于 
      Computers have become a lot faster since we compromised on the
partial MD4 hash which we use currently for performance reasons.

MD5 is a much safer choice, and is inline with both RFC1948 and
other ISS generators (OpenBSD, Solaris, etc.)

Furthermore, only having 24-bits of the sequence number be truly
unpredictable is a very serious limitation.  So the periodic
regeneration and 8-bit counter have been removed.  We compute and
use a full 32-bit sequence number.

For ipv6, DCCP was found to use a 32-bit truncated initial sequence
number (it needs 43-bits) and that is fixed here as well.
Reported-by: NDan Kaminsky <dan@doxpara.com>
Tested-by: NWilly Tarreau <w@1wt.eu>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      6e5714ea
    • D
      crypto: Move md5_transform to lib/md5.c · bc0b96b5
      由 David S. Miller 提交于 
      We are going to use this for TCP/IP sequence number and fragment ID
generation.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      bc0b96b5
    • M
      lib/sha1: use the git implementation of SHA-1 · 1eb19a12
      由 Mandeep Singh Baines 提交于 
      For ChromiumOS, we use SHA-1 to verify the integrity of the root
filesystem.  The speed of the kernel sha-1 implementation has a major
impact on our boot performance.

To improve boot performance, we investigated using the heavily optimized
sha-1 implementation used in git.  With the git sha-1 implementation, we
see a 11.7% improvement in boot time.

10 reboots, remove slowest/fastest.

Before:

  Mean: 6.58 seconds Stdev: 0.14

After (with git sha-1, this patch):

  Mean: 5.89 seconds Stdev: 0.07

The other cool thing about the git SHA-1 implementation is that it only
needs 64 bytes of stack for the workspace while the original kernel
implementation needed 320 bytes.
Signed-off-by: NMandeep Singh Baines <msb@chromium.org>
Cc: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
Cc: Nicolas Pitre <nico@cam.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: David S. Miller <davem@davemloft.net>
Cc: linux-crypto@vger.kernel.org
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      1eb19a12
  27. 06 8月, 2011 1 次提交
  29. 05 8月, 2011 1 次提交
  31. 04 8月, 2011 1 次提交