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  1. 12 7月, 2009 1 次提交
  3. 10 7月, 2009 1 次提交
    • J
      net: adding memory barrier to the poll and receive callbacks · a57de0b4
      由 Jiri Olsa 提交于 
      Adding memory barrier after the poll_wait function, paired with
receive callbacks. Adding fuctions sock_poll_wait and sk_has_sleeper
to wrap the memory barrier.

Without the memory barrier, following race can happen.
The race fires, when following code paths meet, and the tp->rcv_nxt
and __add_wait_queue updates stay in CPU caches.

CPU1                         CPU2

sys_select                   receive packet
  ...                        ...
  __add_wait_queue           update tp->rcv_nxt
  ...                        ...
  tp->rcv_nxt check          sock_def_readable
  ...                        {
  schedule                      ...
                                if (sk->sk_sleep && waitqueue_active(sk->sk_sleep))
                                        wake_up_interruptible(sk->sk_sleep)
                                ...
                             }

If there was no cache the code would work ok, since the wait_queue and
rcv_nxt are opposit to each other.

Meaning that once tp->rcv_nxt is updated by CPU2, the CPU1 either already
passed the tp->rcv_nxt check and sleeps, or will get the new value for
tp->rcv_nxt and will return with new data mask.
In both cases the process (CPU1) is being added to the wait queue, so the
waitqueue_active (CPU2) call cannot miss and will wake up CPU1.

The bad case is when the __add_wait_queue changes done by CPU1 stay in its
cache, and so does the tp->rcv_nxt update on CPU2 side.  The CPU1 will then
endup calling schedule and sleep forever if there are no more data on the
socket.

Calls to poll_wait in following modules were ommited:
	net/bluetooth/af_bluetooth.c
	net/irda/af_irda.c
	net/irda/irnet/irnet_ppp.c
	net/mac80211/rc80211_pid_debugfs.c
	net/phonet/socket.c
	net/rds/af_rds.c
	net/rfkill/core.c
	net/sunrpc/cache.c
	net/sunrpc/rpc_pipe.c
	net/tipc/socket.c
Signed-off-by: NJiri Olsa <jolsa@redhat.com>
Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      a57de0b4
  5. 15 6月, 2009 1 次提交
    • V
      net: annotate struct sock bitfield · a98b65a3
      由 Vegard Nossum 提交于 
      2009/2/24 Ingo Molnar <mingo@elte.hu>:
> ok, this is the last warning i have from today's overnight -tip
> testruns - a 32-bit system warning in sock_init_data():
>
> [    2.610389] NET: Registered protocol family 16
> [    2.616138] initcall netlink_proto_init+0x0/0x170 returned 0 after 7812 usecs
> [    2.620010] WARNING: kmemcheck: Caught 32-bit read from uninitialized memory (f642c184)
> [    2.624002] 010000000200000000000000604990c000000000000000000000000000000000
> [    2.634076]  i i i i i i u u i i i i i i i i i i i i i i i i i i i i i i i i
> [    2.641038]          ^
> [    2.643376]
> [    2.644004] Pid: 1, comm: swapper Not tainted (2.6.29-rc6-tip-01751-g4d1c22c-dirty #885)
> [    2.648003] EIP: 0060:[<c07141a1>] EFLAGS: 00010282 CPU: 0
> [    2.652008] EIP is at sock_init_data+0xa1/0x190
> [    2.656003] EAX: 0001a800 EBX: f6836c00 ECX: 00463000 EDX: c0e46fe0
> [    2.660003] ESI: f642c180 EDI: c0b83088 EBP: f6863ed8 ESP: c0c412ec
> [    2.664003]  DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068
> [    2.668003] CR0: 8005003b CR2: f682c400 CR3: 00b91000 CR4: 000006f0
> [    2.672003] DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000
> [    2.676003] DR6: ffff4ff0 DR7: 00000400
> [    2.680002]  [<c07423e5>] __netlink_create+0x35/0xa0
> [    2.684002]  [<c07443cc>] netlink_kernel_create+0x4c/0x140
> [    2.688002]  [<c072755e>] rtnetlink_net_init+0x1e/0x40
> [    2.696002]  [<c071b601>] register_pernet_operations+0x11/0x30
> [    2.700002]  [<c071b72c>] register_pernet_subsys+0x1c/0x30
> [    2.704002]  [<c0bf3c8c>] rtnetlink_init+0x4c/0x100
> [    2.708002]  [<c0bf4669>] netlink_proto_init+0x159/0x170
> [    2.712002]  [<c0101124>] do_one_initcall+0x24/0x150
> [    2.716002]  [<c0bbf3c7>] do_initcalls+0x27/0x40
> [    2.723201]  [<c0bbf3fc>] do_basic_setup+0x1c/0x20
> [    2.728002]  [<c0bbfb8a>] kernel_init+0x5a/0xa0
> [    2.732002]  [<c0103e47>] kernel_thread_helper+0x7/0x10
> [    2.736002]  [<ffffffff>] 0xffffffff

We fix this false positive by annotating the bitfield in struct
sock.
Reported-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>
      a98b65a3
  7. 11 6月, 2009 1 次提交
    • E
      net: No more expensive sock_hold()/sock_put() on each tx · 2b85a34e
      由 Eric Dumazet 提交于 
      One of the problem with sock memory accounting is it uses
a pair of sock_hold()/sock_put() for each transmitted packet.

This slows down bidirectional flows because the receive path
also needs to take a refcount on socket and might use a different
cpu than transmit path or transmit completion path. So these
two atomic operations also trigger cache line bounces.

We can see this in tx or tx/rx workloads (media gateways for example),
where sock_wfree() can be in top five functions in profiles.

We use this sock_hold()/sock_put() so that sock freeing
is delayed until all tx packets are completed.

As we also update sk_wmem_alloc, we could offset sk_wmem_alloc
by one unit at init time, until sk_free() is called.
Once sk_free() is called, we atomic_dec_and_test(sk_wmem_alloc)
to decrement initial offset and atomicaly check if any packets
are in flight.

skb_set_owner_w() doesnt call sock_hold() anymore

sock_wfree() doesnt call sock_put() anymore, but check if sk_wmem_alloc
reached 0 to perform the final freeing.

Drawback is that a skb->truesize error could lead to unfreeable sockets, or
even worse, prematurely calling __sk_free() on a live socket.

Nice speedups on SMP. tbench for example, going from 2691 MB/s to 2711 MB/s
on my 8 cpu dev machine, even if tbench was not really hitting sk_refcnt
contention point. 5 % speedup on a UDP transmit workload (depends
on number of flows), lowering TX completion cpu usage.
Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      2b85a34e
  9. 09 6月, 2009 1 次提交
  11. 28 5月, 2009 1 次提交
  13. 01 4月, 2009 1 次提交
  15. 27 2月, 2009 1 次提交
  17. 24 2月, 2009 1 次提交
  19. 18 2月, 2009 1 次提交
    • D
      net: Kill skb_truesize_check(), it only catches false-positives. · 92a0acce
      由 David S. Miller 提交于 
      A long time ago we had bugs, primarily in TCP, where we would modify
skb->truesize (for TSO queue collapsing) in ways which would corrupt
the socket memory accounting.

skb_truesize_check() was added in order to try and catch this error
more systematically.

However this debugging check has morphed into a Frankenstein of sorts
and these days it does nothing other than catch false-positives.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      92a0acce
  21. 16 2月, 2009 1 次提交
  23. 13 2月, 2009 1 次提交
  25. 05 2月, 2009 1 次提交
  27. 18 12月, 2008 1 次提交
  29. 26 11月, 2008 2 次提交
  31. 22 11月, 2008 1 次提交
  33. 20 11月, 2008 1 次提交
  35. 17 11月, 2008 1 次提交
    • E
      net: Convert TCP & DCCP hash tables to use RCU / hlist_nulls · 3ab5aee7
      由 Eric Dumazet 提交于 
      RCU was added to UDP lookups, using a fast infrastructure :
- sockets kmem_cache use SLAB_DESTROY_BY_RCU and dont pay the
  price of call_rcu() at freeing time.
- hlist_nulls permits to use few memory barriers.

This patch uses same infrastructure for TCP/DCCP established
and timewait sockets.

Thanks to SLAB_DESTROY_BY_RCU, no slowdown for applications
using short lived TCP connections. A followup patch, converting
rwlocks to spinlocks will even speedup this case.

__inet_lookup_established() is pretty fast now we dont have to
dirty a contended cache line (read_lock/read_unlock)

Only established and timewait hashtable are converted to RCU
(bind table and listen table are still using traditional locking)
Signed-off-by: NEric Dumazet <dada1@cosmosbay.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      3ab5aee7
  37. 14 11月, 2008 1 次提交
    • I
      lockdep: include/linux/lockdep.h - fix warning in net/bluetooth/af_bluetooth.c · e8f6fbf6
      由 Ingo Molnar 提交于 
      fix this warning:

  net/bluetooth/af_bluetooth.c:60: warning: ‘bt_key_strings’ defined but not used
  net/bluetooth/af_bluetooth.c:71: warning: ‘bt_slock_key_strings’ defined but not used

this is a lockdep macro problem in the !LOCKDEP case.

We cannot convert it to an inline because the macro works on multiple types,
but we can mark the parameter used.

[ also clean up a misaligned tab in sock_lock_init_class_and_name() ]

[ also remove #ifdefs from around af_family_clock_key strings - which
  were certainly added to get rid of the ugly build warnings. ]
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      e8f6fbf6
  39. 12 11月, 2008 1 次提交
    • I
      lockdep: include/linux/lockdep.h - fix warning in net/bluetooth/af_bluetooth.c · e25cf3db
      由 Ingo Molnar 提交于 
      fix this warning:

  net/bluetooth/af_bluetooth.c:60: warning: ‘bt_key_strings’ defined but not used
  net/bluetooth/af_bluetooth.c:71: warning: ‘bt_slock_key_strings’ defined but not used

this is a lockdep macro problem in the !LOCKDEP case.

We cannot convert it to an inline because the macro works on multiple types,
but we can mark the parameter used.

[ also clean up a misaligned tab in sock_lock_init_class_and_name() ]

[ also remove #ifdefs from around af_family_clock_key strings - which
  were certainly added to get rid of the ugly build warnings. ]
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      e25cf3db
  41. 29 10月, 2008 1 次提交
    • E
      udp: RCU handling for Unicast packets. · 271b72c7
      由 Eric Dumazet 提交于 
      Goals are :

1) Optimizing handling of incoming Unicast UDP frames, so that no memory
 writes should happen in the fast path.

 Note: Multicasts and broadcasts still will need to take a lock,
 because doing a full lockless lookup in this case is difficult.

2) No expensive operations in the socket bind/unhash phases :
  - No expensive synchronize_rcu() calls.

  - No added rcu_head in socket structure, increasing memory needs,
  but more important, forcing us to use call_rcu() calls,
  that have the bad property of making sockets structure cold.
  (rcu grace period between socket freeing and its potential reuse
   make this socket being cold in CPU cache).
  David did a previous patch using call_rcu() and noticed a 20%
  impact on TCP connection rates.
  Quoting Cristopher Lameter :
   "Right. That results in cacheline cooldown. You'd want to recycle
    the object as they are cache hot on a per cpu basis. That is screwed
    up by the delayed regular rcu processing. We have seen multiple
    regressions due to cacheline cooldown.
    The only choice in cacheline hot sensitive areas is to deal with the
    complexity that comes with SLAB_DESTROY_BY_RCU or give up on RCU."

  - Because udp sockets are allocated from dedicated kmem_cache,
  use of SLAB_DESTROY_BY_RCU can help here.

Theory of operation :
---------------------

As the lookup is lockfree (using rcu_read_lock()/rcu_read_unlock()),
special attention must be taken by readers and writers.

Use of SLAB_DESTROY_BY_RCU is tricky too, because a socket can be freed,
reused, inserted in a different chain or in worst case in the same chain
while readers could do lookups in the same time.

In order to avoid loops, a reader must check each socket found in a chain
really belongs to the chain the reader was traversing. If it finds a
mismatch, lookup must start again at the begining. This *restart* loop
is the reason we had to use rdlock for the multicast case, because
we dont want to send same message several times to the same socket.

We use RCU only for fast path.
Thus, /proc/net/udp still takes spinlocks.
Signed-off-by: NEric Dumazet <dada1@cosmosbay.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      271b72c7
  43. 08 10月, 2008 1 次提交
  45. 23 9月, 2008 1 次提交
  47. 19 9月, 2008 1 次提交
  49. 24 7月, 2008 1 次提交
  51. 17 7月, 2008 1 次提交
  53. 18 6月, 2008 1 次提交
  55. 12 6月, 2008 1 次提交
  57. 14 5月, 2008 1 次提交
  59. 03 5月, 2008 1 次提交
  61. 22 4月, 2008 2 次提交
  63. 16 4月, 2008 1 次提交
  65. 14 4月, 2008 1 次提交
  67. 01 4月, 2008 2 次提交
  69. 29 3月, 2008 3 次提交