linux-toradex.git/include/net/sock.h, branch v3.6

include/net/sock.h: squelch compiler warning in sk_rmem_schedule()

2012-09-17T22:00:38+00:00

This warning:

  In file included from linux/include/linux/tcp.h:227:0,
                   from linux/include/linux/ipv6.h:221,
                   from linux/include/net/ipv6.h:16,
                   from linux/include/linux/sunrpc/clnt.h:26,
                   from linux/net/sunrpc/stats.c:22:
  linux/include/net/sock.h: In function `sk_rmem_schedule':
  linux/nfs-2.6/include/net/sock.h:1339:13: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]

is seen with gcc (GCC) 4.6.3 20120306 (Red Hat 4.6.3-2) using the
-Wextra option.

Commit c76562b6709f ("netvm: prevent a stream-specific deadlock")
accidentally replaced the "size" parameter of sk_rmem_schedule() with an
unsigned int.  This changes the semantics of the comparison in the
return statement.

In sk_wmem_schedule we have syntactically the same comparison, but
"size" is a signed integer.  In addition, __sk_mem_schedule() takes a
signed integer for its "size" parameter, so there is an implicit type
conversion in sk_rmem_schedule() anyway.

Revert the "size" parameter back to a signed integer so that the
semantics of the expressions in both sk_[rw]mem_schedule() are exactly
the same.

Signed-off-by: Chuck Lever 
Signed-off-by: Mel Gorman 
Cc: David Miller 
Cc: Joonsoo Kim 
Cc: David Rientjes 
Cc: Pekka Enberg 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

tcp: Apply device TSO segment limit earlier

2012-08-02T07:19:17+00:00

Cache the device gso_max_segs in sock::sk_gso_max_segs and use it to
limit the size of TSO skbs.  This avoids the need to fall back to
software GSO for local TCP senders.

Signed-off-by: Ben Hutchings 
Signed-off-by: David S. Miller

netvm: prevent a stream-specific deadlock

2012-08-01T01:42:47+00:00

This patch series is based on top of "Swap-over-NBD without deadlocking
v15" as it depends on the same reservation of PF_MEMALLOC reserves logic.

When a user or administrator requires swap for their application, they
create a swap partition and file, format it with mkswap and activate it
with swapon.  In diskless systems this is not an option so if swap if
required then swapping over the network is considered.  The two likely
scenarios are when blade servers are used as part of a cluster where the
form factor or maintenance costs do not allow the use of disks and thin
clients.

The Linux Terminal Server Project recommends the use of the Network Block
Device (NBD) for swap but this is not always an option.  There is no
guarantee that the network attached storage (NAS) device is running Linux
or supports NBD.  However, it is likely that it supports NFS so there are
users that want support for swapping over NFS despite any performance
concern.  Some distributions currently carry patches that support swapping
over NFS but it would be preferable to support it in the mainline kernel.

Patch 1 avoids a stream-specific deadlock that potentially affects TCP.

Patch 2 is a small modification to SELinux to avoid using PFMEMALLOC
	reserves.

Patch 3 adds three helpers for filesystems to handle swap cache pages.
	For example, page_file_mapping() returns page->mapping for
	file-backed pages and the address_space of the underlying
	swap file for swap cache pages.

Patch 4 adds two address_space_operations to allow a filesystem
	to pin all metadata relevant to a swapfile in memory. Upon
	successful activation, the swapfile is marked SWP_FILE and
	the address space operation ->direct_IO is used for writing
	and ->readpage for reading in swap pages.

Patch 5 notes that patch 3 is bolting
	filesystem-specific-swapfile-support onto the side and that
	the default handlers have different information to what
	is available to the filesystem. This patch refactors the
	code so that there are generic handlers for each of the new
	address_space operations.

Patch 6 adds an API to allow a vector of kernel addresses to be
	translated to struct pages and pinned for IO.

Patch 7 adds support for using highmem pages for swap by kmapping
	the pages before calling the direct_IO handler.

Patch 8 updates NFS to use the helpers from patch 3 where necessary.

Patch 9 avoids setting PF_private on PG_swapcache pages within NFS.

Patch 10 implements the new swapfile-related address_space operations
	for NFS and teaches the direct IO handler how to manage
	kernel addresses.

Patch 11 prevents page allocator recursions in NFS by using GFP_NOIO
	where appropriate.

Patch 12 fixes a NULL pointer dereference that occurs when using
	swap-over-NFS.

With the patches applied, it is possible to mount a swapfile that is on an
NFS filesystem.  Swap performance is not great with a swap stress test
taking roughly twice as long to complete than if the swap device was
backed by NBD.

This patch: netvm: prevent a stream-specific deadlock

It could happen that all !SOCK_MEMALLOC sockets have buffered so much data
that we're over the global rmem limit.  This will prevent SOCK_MEMALLOC
buffers from receiving data, which will prevent userspace from running,
which is needed to reduce the buffered data.

Fix this by exempting the SOCK_MEMALLOC sockets from the rmem limit.  Once
this change it applied, it is important that sockets that set
SOCK_MEMALLOC do not clear the flag until the socket is being torn down.
If this happens, a warning is generated and the tokens reclaimed to avoid
accounting errors until the bug is fixed.

[davem@davemloft.net: Warning about clearing SOCK_MEMALLOC]
Signed-off-by: Peter Zijlstra 
Signed-off-by: Mel Gorman 
Acked-by: David S. Miller 
Acked-by: Rik van Riel 
Cc: Trond Myklebust 
Cc: Neil Brown 
Cc: Christoph Hellwig 
Cc: Mike Christie 
Cc: Eric B Munson 
Cc: Sebastian Andrzej Siewior 
Cc: Mel Gorman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

netvm: set PF_MEMALLOC as appropriate during SKB processing

2012-08-01T01:42:46+00:00

In order to make sure pfmemalloc packets receive all memory needed to
proceed, ensure processing of pfmemalloc SKBs happens under PF_MEMALLOC.
This is limited to a subset of protocols that are expected to be used for
writing to swap.  Taps are not allowed to use PF_MEMALLOC as these are
expected to communicate with userspace processes which could be paged out.

[a.p.zijlstra@chello.nl: Ideas taken from various patches]
[jslaby@suse.cz: Lock imbalance fix]
Signed-off-by: Mel Gorman 
Acked-by: David S. Miller 
Cc: Neil Brown 
Cc: Peter Zijlstra 
Cc: Mike Christie 
Cc: Eric B Munson 
Cc: Eric Dumazet 
Cc: Sebastian Andrzej Siewior 
Cc: Mel Gorman 
Cc: Christoph Lameter 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

netvm: allow skb allocation to use PFMEMALLOC reserves

2012-08-01T01:42:46+00:00

Change the skb allocation API to indicate RX usage and use this to fall
back to the PFMEMALLOC reserve when needed.  SKBs allocated from the
reserve are tagged in skb->pfmemalloc.  If an SKB is allocated from the
reserve and the socket is later found to be unrelated to page reclaim, the
packet is dropped so that the memory remains available for page reclaim.
Network protocols are expected to recover from this packet loss.

[a.p.zijlstra@chello.nl: Ideas taken from various patches]
[davem@davemloft.net: Use static branches, coding style corrections]
[sebastian@breakpoint.cc: Avoid unnecessary cast, fix !CONFIG_NET build]
Signed-off-by: Mel Gorman 
Acked-by: David S. Miller 
Cc: Neil Brown 
Cc: Peter Zijlstra 
Cc: Mike Christie 
Cc: Eric B Munson 
Cc: Eric Dumazet 
Cc: Sebastian Andrzej Siewior 
Cc: Mel Gorman 
Cc: Christoph Lameter 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

netvm: allow the use of __GFP_MEMALLOC by specific sockets

2012-08-01T01:42:46+00:00

Allow specific sockets to be tagged SOCK_MEMALLOC and use __GFP_MEMALLOC
for their allocations.  These sockets will be able to go below watermarks
and allocate from the emergency reserve.  Such sockets are to be used to
service the VM (iow.  to swap over).  They must be handled kernel side,
exposing such a socket to user-space is a bug.

There is a risk that the reserves be depleted so for now, the
administrator is responsible for increasing min_free_kbytes as necessary
to prevent deadlock for their workloads.

[a.p.zijlstra@chello.nl: Original patches]
Signed-off-by: Mel Gorman 
Acked-by: David S. Miller 
Cc: Neil Brown 
Cc: Peter Zijlstra 
Cc: Mike Christie 
Cc: Eric B Munson 
Cc: Eric Dumazet 
Cc: Sebastian Andrzej Siewior 
Cc: Mel Gorman 
Cc: Christoph Lameter 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

net: introduce sk_gfp_atomic() to allow addition of GFP flags depending on the individual socket

2012-08-01T01:42:46+00:00

Introduce sk_gfp_atomic(), this function allows to inject sock specific
flags to each sock related allocation.  It is only used on allocation
paths that may be required for writing pages back to network storage.

[davem@davemloft.net: Use sk_gfp_atomic only when necessary]
Signed-off-by: Peter Zijlstra 
Signed-off-by: Mel Gorman 
Acked-by: David S. Miller 
Cc: Neil Brown 
Cc: Mike Christie 
Cc: Eric B Munson 
Cc: Eric Dumazet 
Cc: Sebastian Andrzej Siewior 
Cc: Mel Gorman 
Cc: Christoph Lameter 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

memcg: rename config variables

2012-08-01T01:42:43+00:00

Sanity:

CONFIG_CGROUP_MEM_RES_CTLR -> CONFIG_MEMCG
CONFIG_CGROUP_MEM_RES_CTLR_SWAP -> CONFIG_MEMCG_SWAP
CONFIG_CGROUP_MEM_RES_CTLR_SWAP_ENABLED -> CONFIG_MEMCG_SWAP_ENABLED
CONFIG_CGROUP_MEM_RES_CTLR_KMEM -> CONFIG_MEMCG_KMEM

[mhocko@suse.cz: fix missed bits]
Cc: Glauber Costa 
Acked-by: Michal Hocko 
Cc: Johannes Weiner 
Cc: KAMEZAWA Hiroyuki 
Cc: Hugh Dickins 
Cc: Tejun Heo 
Cc: Aneesh Kumar K.V 
Cc: David Rientjes 
Cc: KOSAKI Motohiro 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

tcp: dont drop MTU reduction indications

2012-07-23T07:58:46+00:00

ICMP messages generated in output path if frame length is bigger than
mtu are actually lost because socket is owned by user (doing the xmit)

One example is the ipgre_tunnel_xmit() calling
icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, htonl(mtu));

We had a similar case fixed in commit a34a101e1e6 (ipv6: disable GSO on
sockets hitting dst_allfrag).

Problem of such fix is that it relied on retransmit timers, so short tcp
sessions paid a too big latency increase price.

This patch uses the tcp_release_cb() infrastructure so that MTU
reduction messages (ICMP messages) are not lost, and no extra delay
is added in TCP transmits.

Reported-by: Maciej Żenczykowski 
Diagnosed-by: Neal Cardwell 
Signed-off-by: Eric Dumazet 
Cc: Nandita Dukkipati 
Cc: Tom Herbert 
Cc: Tore Anderson 
Signed-off-by: David S. Miller

tcp: TCP Small Queues

2012-07-12T01:12:59+00:00

This introduce TSQ (TCP Small Queues)

TSQ goal is to reduce number of TCP packets in xmit queues (qdisc &
device queues), to reduce RTT and cwnd bias, part of the bufferbloat
problem.

sk->sk_wmem_alloc not allowed to grow above a given limit,
allowing no more than ~128KB [1] per tcp socket in qdisc/dev layers at a
given time.

TSO packets are sized/capped to half the limit, so that we have two
TSO packets in flight, allowing better bandwidth use.

As a side effect, setting the limit to 40000 automatically reduces the
standard gso max limit (65536) to 40000/2 : It can help to reduce
latencies of high prio packets, having smaller TSO packets.

This means we divert sock_wfree() to a tcp_wfree() handler, to
queue/send following frames when skb_orphan() [2] is called for the
already queued skbs.

Results on my dev machines (tg3/ixgbe nics) are really impressive,
using standard pfifo_fast, and with or without TSO/GSO.

Without reduction of nominal bandwidth, we have reduction of buffering
per bulk sender :
< 1ms on Gbit (instead of 50ms with TSO)
< 8ms on 100Mbit (instead of 132 ms)

I no longer have 4 MBytes backlogged in qdisc by a single netperf
session, and both side socket autotuning no longer use 4 Mbytes.

As skb destructor cannot restart xmit itself ( as qdisc lock might be
taken at this point ), we delegate the work to a tasklet. We use one
tasklest per cpu for performance reasons.

If tasklet finds a socket owned by the user, it sets TSQ_OWNED flag.
This flag is tested in a new protocol method called from release_sock(),
to eventually send new segments.

[1] New /proc/sys/net/ipv4/tcp_limit_output_bytes tunable
[2] skb_orphan() is usually called at TX completion time,
  but some drivers call it in their start_xmit() handler.
  These drivers should at least use BQL, or else a single TCP
  session can still fill the whole NIC TX ring, since TSQ will
  have no effect.

Signed-off-by: Eric Dumazet 
Cc: Dave Taht 
Cc: Tom Herbert 
Cc: Matt Mathis 
Cc: Yuchung Cheng 
Cc: Nandita Dukkipati 
Signed-off-by: David S. Miller