staging/lustre/ptlrpc: make ptlrpcd threads cpt-aware

staging/lustre/ptlrpc: make ptlrpcd threads cpt-aware

On NUMA systems, the placement of worker threads relative to the
memory they use greatly affects performance. The CPT mechanism can be
used to constrain a number of Lustre thread types, and this change
makes it possible to configure the placement of ptlrpcd threads in a
similar manner.

To simplify the code changes, the global structures used to manage
ptlrpcd threads are changed to one per CPT. In particular this means
there will be one ptlrpcd recovery thread per CPT.

To prevent ptlrpcd threads from wandering all over the system, all
ptlrpcd thread are bound to a CPT. Note that some CPT configuration
is always created, but the defaults are not likely to be correct for
a NUMA system. After discussing the options with Liang Zhen we
decided that we would not bind ptlrpcd threads to specific CPUs,
and rather trust the kernel scheduler to migrate ptlrpcd threads.

With all ptlrpcd threads bound to a CPT, but not to specific CPUs,
the load policy mechanism can be radically simplified:

- PDL_POLICY_LOCAL and PDL_POLICY_ROUND are currently identical.
- PDL_POLICY_ROUND, if fully implemented, would cost us the locality
  we are trying to achieve, so most or all calls using this policy
  would have to be changed to PDL_POLICY_LOCAL.
- PDL_POLICY_PREFERRED is not used, and cannot be implemented without
  binding ptlrpcd threads to individual CPUs.
- PDL_POLICY_SAME is rarely used, and cannot be implemented without
  binding ptlrpcd threads to individual CPUs.

The partner mechanism is also updated, because now all ptlrpcd
threads are "bound" threads. The only difference between the various
bind policies, PDB_POLICY_NONE, PDB_POLICY_FULL, PDB_POLICY_PAIR, and
PDB_POLICY_NEIGHBOR, is the number of partner threads. The bind
policy is replaced with a tunable that directly specifies the size of
the groups of ptlrpcd partner threads.

Ensure that the ptlrpc_request_set for a ptlrpcd thread is created on
the same CPT that the thread will work on. When threads are bound to
specific nodes and/or CPUs in a NUMA system, it pays to ensure that
the datastructures used by these threads are also on the same node.

Visible changes:

* ptlrpcd thread names include the CPT number, for example
  "ptlrpcd_02_07". In this case the "07" is relative to the CPT, and
  not a CPU number.

Tunables added:

* ptlrpcd_cpts (string): A CPT string describing the CPU partitions
  that ptlrpcd threads should run on. Used to make ptlrpcd threads
  run on a subset of all CPTs.

* ptlrpcd_per_cpt_max (int): The maximum number of ptlrpcd threads
  to run in a CPT.

* ptlrpcd_partner_group_size (int): The desired number of threads
  in each ptlrpcd partner thread group. Default is 2, corresponding
  to the old PDB_POLICY_PAIR. A negative value makes all ptlrpcd
  threads in a CPT partners of each other.

Tunables obsoleted:

* max_ptlrpcds: The new ptlrcpd_per_cpt_max can be used to obtain the
  same effect.

* ptlrpcd_bind_policy: The new ptlrpcd_partner_group_size can be used
  to obtain the same effect.

Internal interface changes:

* pdb_policy_t and related code have been removed. Groups of partner
  ptlrpcd threads are still created, and all threads in a partner
  group are bound on the same CPT. The ptlrpcd threads bound to a
  CPT are typically divided into several partner groups. The partner
  groups on a CPT all have an equal number of ptlrpcd threads.

* pdl_policy_t and related code have been removed. Since ptlrpcd
  threads are not bound to a specific CPU, all the code that avoids
  scheduling on the current CPU (or attempts to do so) has been
  removed as non-functional. A simplified form of PDL_POLICY_LOCAL
  is kept as the only load policy.

* LIOD_BIND and related code have been removed. All ptlrpcd threads
  are now bound to a CPT, and no additional binding policy is
  implemented.

* ptlrpc_prep_set(): Changed to allocate a ptlrpc_request_set
  on the current CPT.

* ptlrpcd(): If an error is encountered before entering the main loop
  store the error in pc_error before exiting.

* ptlrpcd_start(): Check pc_error to verify that the ptlrpcd thread
  has successfully entered its main loop.

* ptlrpcd_init(): Initialize the struct ptlrpcd_ctl for all threads
  for a CPT before starting any of them. This closes a race during
  startup where a partner thread could reference a non-initialized
  struct ptlrpcd_ctl.

Signed-off-by: Olaf Weber <olaf@sgi.com>
Reviewed-on: http://review.whamcloud.com/13972
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-6325
Reviewed-by: Grégoire Pichon <gregoire.pichon@bull.net>
Reviewed-by: Stephen Champion <schamp@sgi.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>