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49 Коммитов

Автор SHA1 Сообщение Дата
Jeff Squyres
e6ed7c9f4d Avoid trivial "don't mix declarations and code" compiler warning
This commit was SVN r29714.
2013-11-15 21:31:10 +00:00
Jeff Squyres
98ff91cfeb Refs trac:3091
Gah!  The "device" variable isn't used at all in this loop (my eye
glossed over the next line and thought that "device" was used in the
free() statement, but it's actually "devices" -- not "device").

This commit was SVN r29665.

The following Trac tickets were found above:
  Ticket 3091 --> https://svn.open-mpi.org/trac/ompi/ticket/3091
2013-11-12 23:01:04 +00:00
Jeff Squyres
7cb31111a6 Refs trac:3901
Feedback from Dave's review.

This commit was SVN r29664.

The following Trac tickets were found above:
  Ticket 3901 --> https://svn.open-mpi.org/trac/ompi/ticket/3901
2013-11-12 22:51:20 +00:00
Jeff Squyres
5a940f5ee7 Arrgh -- remove debugging printf.
This commit was SVN r29657.
2013-11-11 22:44:28 +00:00
Jeff Squyres
e20217eccc Expand the "btl_usnic" MPI_T enumeration to have strings of the form:
<usnic device name>,<eth device>,<ip address>/<CIDR prefix>

For example:

   usnic_0,eth4,10.1.0.15/16

This is just handy for mapping the usnic_X device back to the IP
network to which it corresponds.

This commit was SVN r29656.
2013-11-11 22:25:30 +00:00
Dave Goodell
82db913490 usnic: fix module_recv_buffers perf regression
Cisco v1.6 git commit 913ec6c and upstream trunk r29593 (segfault fix)
introduced a performance regression by inadvertently disabling the
`module_recv_buffers` functionality.  With those changes in place, the
`btl_usnic_recv.c` logic would end up mallocing a buffer that should
have otherwise come from a `module_recv_buffers` pool.  It also resulted
in a small, bounded memory leak (128 buffers at each power-of-two size
interval).

The new version just places the buffer after the free list item with a
flexible array member.  I bumped the pool to allocate all 128 elements
up front because the deferred allocation was modestly impacting IMB
Sendrecv performance at a few sizes.

Reviewed-by: Reese Faucette <rfaucett@cisco.com>

This commit was SVN r29631.

The following SVN revision numbers were found above:
  r29593 --> open-mpi/ompi@1ed9b8ff43
2013-11-07 01:27:31 +00:00
Jeff Squyres
e28261898d Per discussion on the devel list, rename the btl_usnic_devices MPI_T
state pvar to be btl_usnic (i.e., the best suggestion so far).

See http://www.open-mpi.org/community/lists/devel/2013/11/13188.php
for more detail.

This commit was SVN r29614.
2013-11-06 06:19:03 +00:00
Dave Goodell
1ed9b8ff43 usnic: fix segfault at finalize time
Without this commit, if you run IMB pingpong between two nodes with only
one usnic selected (e.g., via `--mca btl_usnic_if_include usnic_0`) then
the run will seem fine but will segfault at MPI_Finalize time.

This behavior has happened since Cisco v1.6 git commit ec7ddf8, upstream
trunk r29484, and upstream v1.7 r29507.

Root cause was that the free list element was being used as the recv
buffer instead of the data buffer associated with the element.  So the
reassembly code would stomp all over the free list element, which would
cause the destructor to explode when the free list attempted to clean up
all of its elements.  This surprisingly did not cause any other problems
until now.

Reviewed-by: Reese Faucette <rfaucett@cisco.com>

This commit was SVN r29593.

The following SVN revision numbers were found above:
  r29484 --> open-mpi/ompi@a6ed232a10
  r29507 --> open-mpi/ompi@790d269ce8
2013-11-04 22:52:14 +00:00
Dave Goodell
73a943492c usnic: pack via convertor on the fly
If we need to use a convertor, go back to stashing that convertor in the
frag and populating segments "on the fly" (in
ompi_btl_usnic_module_progress_sends).  Previously we would pack into a
chain of chunk segments at prepare_src time, unnecessarily consuming
additional memory.

Reviewed-by: Jeff Squyres <jsquyres@cisco.com>
Reviewed-by: Reese Faucette <rfaucett@cisco.com>

This commit was SVN r29592.
2013-11-04 22:52:03 +00:00
Dave Goodell
71d0d73575 usnic: refactor callback invocation
This makes it a little easier to see what's happening with callbacks to
the PML.

Reviewed-by: Jeff Squyres <jsquyres@cisco.com>
Reviewed-by: Reese Faucette <rfaucett@cisco.com>

This commit was SVN r29591.
2013-11-04 22:51:48 +00:00
Dave Goodell
4c791e21d2 usnic: add MSGDEBUG1_OUT/MSGDEBUG2_OUT macros
This includes suppressing picky-mode warnings about __VA_ARGS__, which
we know are supported by any compilers we care about.

Reviewed-by: Jeff Squyres <jsquyres@cisco.com>
Reviewed-by: Reese Faucette <rfaucett@cisco.com>

This commit was SVN r29590.
2013-11-04 22:51:35 +00:00
Dave Goodell
825686a205 usnic: certain send frag members are immutable
Ensure that they never are touched by checking in their destructors.

Reviewed-by: Jeff Squyres <jsquyres@cisco.com>
Reviewed-by: Reese Faucette <rfaucett@cisco.com>

This commit was SVN r29589.
2013-11-04 22:51:24 +00:00
Jeff Squyres
6569019b06 Move all usNIC stats to _stats.c|h and export them as MPI_T pvars.
This commit moves all the module stats into their own struct so that
the stats only need to appear as a single line in the module_t
definition, and then moves all the logic for reporting the stats into
btl_usnic_stats.c|h.

Further, the stats are now exported as MPI_T_BIND_NO_OBJECT entities
(i.e., not bound to any particular MPI handle), and are marked as
READONLY and CONTINUOUS.  They currently all default to verbose level
5 ("Application tuner / detailed", according to
https://svn.open-mpi.org/trac/ompi/wiki/MCAParamLevels).

Most of the statistics are counters, but a small number are high
watermark values.  Due to how counters are reported via MPI_T, none of
the counters are exported through MPI_T if the MCA param
btl_usnic_stats_relative=1 (i.e., the module resets the stats back to
zero at a given frequency).

When MPI_T_pvar_handle_alloc() is invoked on any of these pvars, it
will return a count that is equal to the number of active usnic BTL
modules.  The values returned for any given pvar (e.g.,
num_total_sends) are an array containing one value for each active
usnic BTL module.  The ordering of values in the array is both
consistent across all usnic pvars and stable throughout a single job:
array slot 0 corresponds to module X, array slot 1 corresponds to
module Y, etc.

Mapping which array slot corresponds to which underlying Linux usnic_X
device works as follows:

 * The btl_usnic_devices MPI_T state pvar is associated with a
   btl_usnic_device MPI_T enum, and be obtained via
   MPI_T_pvar_get_info().
 * If all usNIC pvars are of length N, the values [0,N) in the
   btl_usnic_device enum are associated with strings of the
   corresponding underlying Linux device.

For exampe, to look up which Linux device is reported in all usNIC
pvars' array slot 1, look up the int value 1 in the btl_usnic_devices
enum.  Its corresponding string value is underlying Linux device name
(e.g., "usnic_1").

cmr=v1.7.4:subject="usnic BTL MPI_T pvars"

This commit was SVN r29545.
2013-10-28 22:23:08 +00:00
Dave Goodell
d969cfa513 usnic: correctly clean up verbs resources
Due to deallocation ordering (and an entirely missed deallocation), we
were leaking modest amounts of memory inside libusnic_verbs.

Reviewed-by: Jeff Squyres <jsquyres@cisco.com>

This commit was SVN r29485.
2013-10-23 15:51:33 +00:00
Dave Goodell
a6ed232a10 usnic: fix several memory leaks
- some free lists simply were not being OBJ_DESTRUCTed, so they never
  freed their internal memory

- channel->recv_segs.ctx was being assigned in a way that got clobbered
  by ompi_free_list_init_new, so the cleanup code that relied on it
  being set never ran

- numerous other ".ctx" assignments were similarly ineffectual and were
  not being consumed, so I deleted them

Reviewed-by: Jeff Squyres <jsquyres@cisco.com>

This commit was SVN r29484.
2013-10-23 15:51:22 +00:00
Dave Goodell
c9b2343982 usnic: add ompi_btl_usnic_component_debug helper
This new routine can be called in exceptional situations, either
conditionally in BTL code or from a debugger, to help with debugging in
cases where MSGDEBUG1/2 or stats logging are impractical but more detail
is needed.

Reviewed-by: Jeff Squyres <jsquyres@cisco.com>

This commit was SVN r29483.
2013-10-23 15:51:11 +00:00
Dave Goodell
d0b7d125b2 usnic: refactor usnic_stats_callback
Pull the bulk of the functionality out into a new routine,
ompi_btl_usnic_print_stats, which can be used in other debugging
contexts.  This also lets us eliminate the module->final_stats state
tracking.

Reviewed-by: Jeff Squyres <jsquyres@cisco.com>

This commit was SVN r29482.
2013-10-23 15:50:57 +00:00
Jeff Squyres
0fb8edd720 Trivial comment change
This commit was SVN r29480.
2013-10-23 10:15:18 +00:00
Jeff Squyres
b5e2ae86ad Remove all of our "to-do" items from the README.txt.
This commit was SVN r29424.
2013-10-11 16:43:56 +00:00
Dave Goodell
a42fa78da7 usnic: SEGV in OSU benchmarks
Prevent frag from being freed out from under us in the case
the PML callback routine calls usnic_free().  We accomplish this
by delaying decrement of sf_bytes_to_ack until after the callback is
performed, since sf_bytes_to_ack == 0 is condition of freeing the frag.

Fixes Cisco bug CSCuj45094.

Authored-by: Reese Faucette <rfaucett@cisco.com>

cmr=v1.7.3

This commit was SVN r29264.
2013-09-26 21:48:04 +00:00
Jeff Squyres
74d1278f48 btl_usnic_util.c:ompi_btl_usnic_util_abort() also passes in the strerror().
This commit was SVN r29188.
2013-09-17 12:35:51 +00:00
Reese Faucette
8f235e6977 usnic: wrong SG entry used to compute length for small put()s
This commit was SVN r29186.
2013-09-17 08:18:02 +00:00
Reese Faucette
651d61f1a3 Clean up debugging logging a bit.
MSGDEBUG2 now means "print a one-liner for all PML calls into BTL, and
also when BTL calls PML with a recv completion (not send completions)"
MSGDEBUG1 means print more internal gory detail
MSGDEBUG is gone, replaced by MSGDEBUG1

In the process also found that PUT_DEST style fragments could
potentially be leaked in usnic_free() since send_fragment tests were
being applied to see if it was eligible to be freed.

This commit was SVN r29185.
2013-09-17 07:29:40 +00:00
Reese Faucette
f35d9b50e3 Cisco CSCuj22803: fixes for Bsend
changes required to support MPI_Bsend().  Introduces concept of
attaching a buffer to a large segment that the PML can scribble into and
we will send from.  The reason we don't use a pinned buffer and send
directly from that is that usnic_verbs does not (yes) support num_sge>1
for regular sends.  This means the data gets copied twice, but that is
unavoidable.

changed the logic in handle_large_send to be more sensible

Incorporated David's review comments

This commit was SVN r29184.
2013-09-17 07:27:39 +00:00
Reese Faucette
25b5c84d0f Cisco CSCuj13135: Data corruption in MPI_Bsend_ator_c
Do not assume that the "size" passed to alloc_send() will be the same as
the size of the message the resulting fragment will hold when
usnic_send() is called.  This means usnic_send()/usnic_put() can never
trust any pre-computed size values, and are only allowed to look at the
lengths and pointers of the elements in the desc SG list.

This commit was SVN r29183.
2013-09-17 07:25:05 +00:00
Reese Faucette
b9103c0f66 Cisco CSCuj12524: c_put_big segfault
- usnic_free() cannot free the fragment until ACK is received

This commit was SVN r29182.
2013-09-17 07:23:15 +00:00
Reese Faucette
89b5f0899b Cisco CSCuj12520: various problems running c_fence_put_1
- tag needs to be sent in *our* header, not the PML header
- usnic_alloc() should return smaller value if too much data requested
- be careful about callbacks vs removing items from lists
  (we need to remove from outr lists *before* the callback)
- improve send callback handling
- add some more MSGDEBUG2 logging and cleanup

This commit was SVN r29181.
2013-09-17 07:20:44 +00:00
Jeff Squyres
c9f05a2664 Delineate OMPI_FREE_LIST_*_MT separately.
The FREE_LIST_*_MT stuff was introduced on the SVN trunk in r28722
(2013-07-04), but so far, has not been merged into the v1.7 branch yet
(2013-09-06).  So put it in its own #ifdef, rather than defining it
based on OMPI_MAJOR_VERSION/OMPI_MINOR_VERSION.

This commit was SVN r29148.

The following SVN revision numbers were found above:
  r28722 --> open-mpi/ompi@c9e5ab9ed1
2013-09-06 19:22:56 +00:00
Jeff Squyres
e02cc0a7ec No need for this header file.
This commit was SVN r29147.
2013-09-06 19:22:28 +00:00
Jeff Squyres
c53b0890cf Ensure that btl_usnic_compat.h is in the tarball.
This commit was SVN r29140.
2013-09-06 15:53:56 +00:00
Dave Goodell
75fa28c303 usnic: v1.6<->trunk unification, trunk side
The Cisco-maintained v1.6 port of the usnic BTL has diverged from the
upstream trunk and v1.7 branches.  This commit adjusts the trunk to more
closely match the v1.6 branch to simplify future merging and
cherry-picking.

The usnic MCA parameters also need work on this side.

Should be included in usnic v1.7.3 roll-up CMR (refs trac:3760)

This commit was SVN r29138.

The following Trac tickets were found above:
  Ticket 3760 --> https://svn.open-mpi.org/trac/ompi/ticket/3760
2013-09-06 03:21:34 +00:00
Dave Goodell
a669bd01e6 usnic: revamp convertor handling.
The fix for the HPL SEGV was incorrect because it assumed the
prepare_src() routine was always allowed to return "bytes processed"
less than the requested "bytes to send".  It turns out this is only true
if the convertor is what limits the size, we are not allowed to limit
the data sent for our own reasons, else we break login in the upper
layers.

This means we need to learn the number of bytes out of the size
requested the convertor will give us, no matter how big the size is.
Unfortunately, this is a destructive test, and (currently) the only way to
learn that number is to actually have the convertor copy the data out into
buffers.

This change implements this, copying the entire data out into a chain of
send segments which are attached to the large send fragment.  Now we can
always return the proper size value to the PML.

Fixes Cisco bug CSCuj08024

Authored-by: Reese Faucette <rfaucett@cisco.com>

Should be included in usnic v1.7.3 roll-up CMR (refs trac:3760)

This commit was SVN r29137.

The following Trac tickets were found above:
  Ticket 3760 --> https://svn.open-mpi.org/trac/ompi/ticket/3760
2013-09-06 03:21:21 +00:00
Dave Goodell
0ef8336502 new bookkeeping code should return value indicating whether packet is good or not.
Authored-by: Reese Faucette <rfaucett@cisco.com>

Should be included in usnic v1.7.3 roll-up CMR (refs trac:3760)

This commit was SVN r29136.

The following Trac tickets were found above:
  Ticket 3760 --> https://svn.open-mpi.org/trac/ompi/ticket/3760
2013-09-06 03:19:32 +00:00
Dave Goodell
122890c2fd usnic: "bookeeping" --> "bookkeeping"
Should be included in usnic v1.7.3 roll-up CMR (refs trac:3760)

This commit was SVN r29135.

The following Trac tickets were found above:
  Ticket 3760 --> https://svn.open-mpi.org/trac/ompi/ticket/3760
2013-09-06 03:19:20 +00:00
Dave Goodell
0df6ed4acc usnic: squash warnings from perf improvements
Should be included in usnic v1.7.3 roll-up CMR (refs trac:3760)

This commit was SVN r29134.

The following Trac tickets were found above:
  Ticket 3760 --> https://svn.open-mpi.org/trac/ompi/ticket/3760
2013-09-06 03:19:08 +00:00
Dave Goodell
6dc54d372d usnic: Basket of performance changes including:
- round segment buffer allocation to cache-line
    - split some routines into an inline fast section and a called
      slower section
    - introduce receive fastpath in component_progress that:
        o returns immediately if there is a packet available on priority
          queue and fastpath is enabled
        o disables fastpath for 1 time after use to provide fairness to
          other processing
        o defers receive buffer posting
        o defers bookeeping for receive until next call
          to usnic_component_progress

Authored-by: Reese Faucette <rfaucett@cisco.com>

Should be included in usnic v1.7.3 roll-up CMR (refs trac:3760)

This commit was SVN r29133.

The following Trac tickets were found above:
  Ticket 3760 --> https://svn.open-mpi.org/trac/ompi/ticket/3760
2013-09-06 03:18:57 +00:00
Dave Goodell
9cab9777d9 usnic: properly destroy embedded small send frag
Without this, an `--enable-debug` build would hit an assertion in the
list code when run under valgrind with `--malloc-fill=0xff` or any other
case where malloc returned non-zeroed buffers.

Also allow the normal OBJ_ machinery to handle the constructor
invocation ordering for us instead of doing it by hand (which could have
led to future bugs).

Reviewed-by: jsquyres@cisco.com

cmr=v1.7.4

Depends on trunk functionality in r29095 and r29096.  Refs trac:3740,#3741.

This commit was SVN r29127.

The following SVN revision numbers were found above:
  r29095 --> open-mpi/ompi@d1b5940e97
  r29096 --> open-mpi/ompi@a552921171

The following Trac tickets were found above:
  Ticket 3740 --> https://svn.open-mpi.org/trac/ompi/ticket/3740
2013-09-04 20:59:12 +00:00
Dave Goodell
c5a7e8a079 usnic: stomp format specifier warnings
The usnic BTL now builds cleanly under `--enable-picky` when `MSGDEBUG1`
is set.

Reviewed-by: jsquyres

cmr=v1.7.4:reviewer=jsquyres

This commit was SVN r29097.
2013-08-29 23:24:14 +00:00
Dave Goodell
dd82bd3c19 usnic: fix invalid rfstart initialization
endpoint_rfstart was being initialized from a value which was not yet
set.  Also ensure that rfstart is a valid index in the range
0..WINDOW_SIZE-1, since it is used as the index into endpoint_rcvd_segs,
which has WINDOW_SIZE elements.

Without this change there is significant risk of memory corruption or
segfaults, resulting in hangs or crashes, if malloc ever returns us a
value >=WINDOW_SIZE (4096).  Right now we seem to be getting lucky that
the malloc is returning zero-pages to us when we are allocating endpoint
structures (possibly because the freelist performs a single large
allocation for all endpoints).

Fixes Cisco bug CSCui88781.

Reviewed-by: rfaucett@cisco.com
Reviewed-by: jsquyres@cisco.com

cmr=v1.7.3:reviewer=jsquyres

This commit was SVN r29075.
2013-08-27 22:43:20 +00:00
Ralph Castain
45e695928f As per the email discussion, revise the sparse handling of hostnames so that we avoid potential infinite loops while allowing large-scale users to improve their startup time:
* add a new MCA param orte_hostname_cutoff to specify the number of nodes at which we stop including hostnames. This defaults to INT_MAX => always include hostnames. If a value is given, then we will include hostnames for any allocation smaller than the given limit.

* remove ompi_proc_get_hostname. Replace all occurrences with a direct link to ompi_proc_t's proc_hostname, protected by appropriate "if NULL"

* modify the OMPI-ORTE integration component so that any call to modex_recv automatically loads the ompi_proc_t->proc_hostname field as well as returning the requested info. Thus, any process whose modex info you retrieve will automatically receive the hostname. Note that on-demand retrieval is still enabled - i.e., if we are running under direct launch with PMI, the hostname will be fetched upon first call to modex_recv, and then the ompi_proc_t->proc_hostname field will be loaded

* removed a stale MCA param "mpi_keep_peer_hostnames" that was no longer used anywhere in the code base

* added an envar lookup in ess/pmi for the number of nodes in the allocation. Sadly, PMI itself doesn't provide that info, so we have to get it a different way. Currently, we support PBS-based systems and SLURM - for any other, rank0 will emit a warning and we assume max number of daemons so we will always retain hostnames

This commit was SVN r29052.
2013-08-20 18:59:36 +00:00
Jeff Squyres
b30ad28276 Remove some unused variables and an unused goto label.
This commit was SVN r29044.
2013-08-19 16:18:35 +00:00
Ralph Castain
611d7f9f6b When we direct launch an application, we rely on PMI for wireup support. In doing so, we lose the de facto data compression we get from the ORTE modex since we no longer get all the wireup info from every proc in a single blob. Instead, we have to iterate over all the procs, calling PMI_KVS_get for every value we require.
This creates a really bad scaling behavior. Users have found a nearly 20% launch time differential between mpirun and PMI, with PMI being the slower method. Some of the problem is attributable to poor exchange algorithms in RM's like Slurm and Alps, but we make things worse by calling "get" so many times.

Nathan (with a tad advice from me) has attempted to alleviate this problem by reducing the number of "get" calls. This required the following changes:

* upon first request for data, have the OPAL db pmi component fetch and decode *all* the info from a given remote proc. It turned out we weren't caching the info, so we would continually request it and only decode the piece we needed for the immediate request. We now decode all the info and push it into the db hash component for local storage - and then all subsequent retrievals are fulfilled locally

* reduced the amount of data by eliminating the exchange of the OMPI_ARCH value if heterogeneity is not enabled. This was used solely as a check so we would error out if the system wasn't actually homogeneous, which was fine when we thought there was no cost in doing the check. Unfortunately, at large scale and with direct launch, there is a non-zero cost of making this test. We are open to finding a compromise (perhaps turning the test off if requested?), if people feel strongly about performing the test

* reduced the amount of RTE data being automatically fetched, and fetched the rest only upon request. In particular, we no longer immediately fetch the hostname (which is only used for error reporting), but instead get it when needed. Likewise for the RML uri as that info is only required for some (not all) environments. In addition, we no longer fetch the locality unless required, relying instead on the PMI clique info to tell us who is on our local node (if additional info is required, the fetch is performed when a modex_recv is issued).

Again, all this only impacts direct launch - all the info is provided when launched via mpirun as there is no added cost to getting it

Barring objections, we may move this (plus any required other pieces) to the 1.7 branch once it soaks for an appropriate time.

This commit was SVN r29040.
2013-08-17 00:49:18 +00:00
Jeff Squyres
c09ec204ad Change usNIC BTL to always use small fragments when there is a
non-contiguous converter.  We can't "convert on the fly" because the #
of bytes requested may not divide evenly into the convertor data type.

This commit was SVN r29014.
2013-08-11 17:04:13 +00:00
Jeff Squyres
87910daf51 Fix a collection of bugs found by QA and Coverity, and make some minor
improvements:

* Fix minor memory leaks during component_init
* Ensure that an initialization loop does not underflow an unsigned int
* Improve mlock limit checking
* Fix set of BTL modules created during component_init when failing to
  get QP resources or otherwise excluding some (but not all) usnic
  verbs devices
* Fix/improve error messages to be consistent with other Cisco
  documentation
* Randomize the initial sliding window sequence number so that we
  silently drop incoming frames from previous jobs that still have
  existant processes in the middle of dying (and are still
  transmitting) 
* Ensure we don't break out of add_procs too soon and create an
  asymetrical view of what interfaces are available

This commit was SVN r28975.
2013-08-01 16:56:15 +00:00
Jeff Squyres
f7337b8f77 Correct faulty max payload and MTU computations (and update some
debugging that helped us find those).

This commit was SVN r28942.
2013-07-24 16:06:28 +00:00
Jeff Squyres
5323051047 Use sysfs to check MPI has enough VFs, QPs, and CQs
Use the new sysfs files to check that there are enough VFs, QPs, and
CQs for all the MPI processes on this server.
    
Move the checking code into its own subroutine to make it smaller and
easier to read/grok.

This commit was SVN r28937.
2013-07-24 00:38:32 +00:00
Jeff Squyres
b437041aeb Update one more comment.
This commit was SVN r28908.
2013-07-22 17:29:00 +00:00
Jeff Squyres
4b6006402d Use the RTE framework instead of calling ORTE directly.
Brian (rightfully) hit me on the head with the
don't-use-ORTE-use-the-rte-framework clue bat; the usnic BTL now
nicely plays with the RTE framework.

This commit was SVN r28907.
2013-07-22 17:28:23 +00:00
Jeff Squyres
194b285447 First commit of the Cisco usNIC BTL.
This BTL accesses the Cisco usNIC Linux device via the Linux verbs
API via Unreliable Datagram queue pairs.  A few noteworthy points:

 * This BTL does most of its own fragmentation; it tells the PML that
   it has a very high max_send_size (much higher than the network
   MTU).
 * Since UD fragments are, by definition, unreliable, the usnic BTL
   handles all of its own reliability via a sliding window approach
   using the opal_hotel construct and many tricks stolen from the
   corpus of knowledge surrounding efficient TCP.
 * There is a fun PML latency-metric based optimization for NUMA
   awareness of short messages.
 * Note that this is ''not'' a generic UD verbs BTL; it is specific to
   the Cisco usNIC device.

This commit was SVN r28879.
2013-07-19 22:13:58 +00:00