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  1. 05 Jan, 2015 12 commits
  3. 03 Jan, 2015 10 commits
    • David S. Miller's avatar
      Merge branch 'rhashtable-next' · 7beceebf
      David S. Miller authored 
      Thomas Graf says:

====================
rhashtable: Per bucket locks & deferred table resizing

Prepares for and introduces per bucket spinlocks and deferred table
resizing. This allows for parallel table mutations in different hash
buckets from atomic context. The resizing occurs in the background
in a separate worker thread while lookups, inserts, and removals can
continue.

Also modified the chain linked list to be terminated with a special
nulls marker to allow entries to move between multiple lists.

Last but not least, reintroduces lockless netlink_lookup() with
deferred Netlink socket destruction to avoid the side effect of
increased netlink_release() runtime.
====================
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      7beceebf
    • Thomas Graf's avatar
      netlink: Lockless lookup with RCU grace period in socket release · 21e4902a
      Thomas Graf authored 
      Defers the release of the socket reference using call_rcu() to
allow using an RCU read-side protected call to rhashtable_lookup()

This restores behaviour and performance gains as previously
introduced by e341694e ("netlink: Convert netlink_lookup() to use
RCU protected hash table") without the side effect of severely
delayed socket destruction.
Signed-off-by: default avatarThomas Graf <tgraf@suug.ch>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      21e4902a
    • Thomas Graf's avatar
      rhashtable: Supports for nulls marker · f89bd6f8
      Thomas Graf authored 
      In order to allow for wider usage of rhashtable, use a special nulls
marker to terminate each chain. The reason for not using the existing
nulls_list is that the prev pointer usage would not be valid as entries
can be linked in two different buckets at the same time.

The 4 nulls base bits can be set through the rhashtable_params structure
like this:

struct rhashtable_params params = {
        [...]
        .nulls_base = (1U << RHT_BASE_SHIFT),
};

This reduces the hash length from 32 bits to 27 bits.
Signed-off-by: default avatarThomas Graf <tgraf@suug.ch>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      f89bd6f8
    • Thomas Graf's avatar
      rhashtable: Per bucket locks & deferred expansion/shrinking · 97defe1e
      Thomas Graf authored 
      Introduces an array of spinlocks to protect bucket mutations. The number
of spinlocks per CPU is configurable and selected based on the hash of
the bucket. This allows for parallel insertions and removals of entries
which do not share a lock.

The patch also defers expansion and shrinking to a worker queue which
allows insertion and removal from atomic context. Insertions and
deletions may occur in parallel to it and are only held up briefly
while the particular bucket is linked or unzipped.

Mutations of the bucket table pointer is protected by a new mutex, read
access is RCU protected.

In the event of an expansion or shrinking, the new bucket table allocated
is exposed as a so called future table as soon as the resize process
starts.  Lookups, deletions, and insertions will briefly use both tables.
The future table becomes the main table after an RCU grace period and
initial linking of the old to the new table was performed. Optimization
of the chains to make use of the new number of buckets follows only the
new table is in use.

The side effect of this is that during that RCU grace period, a bucket
traversal using any rht_for_each() variant on the main table will not see
any insertions performed during the RCU grace period which would at that
point land in the future table. The lookup will see them as it searches
both tables if needed.

Having multiple insertions and removals occur in parallel requires nelems
to become an atomic counter.
Signed-off-by: default avatarThomas Graf <tgraf@suug.ch>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      97defe1e
    • Thomas Graf's avatar
      spinlock: Add spin_lock_bh_nested() · 113948d8
      Thomas Graf authored 
      Signed-off-by: default avatarThomas Graf <tgraf@suug.ch>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      113948d8
    • Thomas Graf's avatar
      nft_hash: Remove rhashtable_remove_pprev() · 897362e4
      Thomas Graf authored 
      The removal function of nft_hash currently stores a reference to the
previous element during lookup which is used to optimize removal later
on. This was possible because a lock is held throughout calling
rhashtable_lookup() and rhashtable_remove().

With the introdution of deferred table resizing in parallel to lookups
and insertions, the nftables lock will no longer synchronize all
table mutations and the stored pprev may become invalid.

Removing this optimization makes removal slightly more expensive on
average but allows taking the resize cost out of the insert and
remove path.
Signed-off-by: default avatarThomas Graf <tgraf@suug.ch>
Cc: netfilter-devel@vger.kernel.org
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      897362e4
    • Thomas Graf's avatar
      rhashtable: Factor out bucket_tail() function · b8e1943e
      Thomas Graf authored 
      Subsequent patches will require access to the bucket tail. Access
to the tail is relatively cheap as the automatic resizing of the
table should keep the number of entries per bucket to no more
than 0.75 on average.
Signed-off-by: default avatarThomas Graf <tgraf@suug.ch>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      b8e1943e
    • Thomas Graf's avatar
      rhashtable: Convert bucket iterators to take table and index · 88d6ed15
      Thomas Graf authored 
      This patch is in preparation to introduce per bucket spinlocks. It
extends all iterator macros to take the bucket table and bucket
index. It also introduces a new rht_dereference_bucket() to
handle protected accesses to buckets.

It introduces a barrier() to the RCU iterators to the prevent
the compiler from caching the first element.

The lockdep verifier is introduced as stub which always succeeds
and properly implement in the next patch when the locks are
introduced.
Signed-off-by: default avatarThomas Graf <tgraf@suug.ch>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      88d6ed15
    • Thomas Graf's avatar
      rhashtable: Use rht_obj() instead of manual offset calculation · a4b18cda
      Thomas Graf authored 
      Signed-off-by: default avatarThomas Graf <tgraf@suug.ch>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      a4b18cda
    • Thomas Graf's avatar
      rhashtable: Do hashing inside of rhashtable_lookup_compare() · 8d24c0b4
      Thomas Graf authored 
      Hash the key inside of rhashtable_lookup_compare() like
rhashtable_lookup() does. This allows to simplify the hashing
functions and keep them private.
Signed-off-by: default avatarThomas Graf <tgraf@suug.ch>
Cc: netfilter-devel@vger.kernel.org
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      8d24c0b4
  5. 02 Jan, 2015 18 commits
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