kirr has uploaded this change for review.

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trx_toolkit/data_msg: Disable cyclic GC support for RxMsg

Checking profiling turned out that there are frequent
PyObject_GC_Track/PyObject_GC_UnTrack for RxMsg because BurstForwarder
creates RxMsg often: to forward on received TxMsg burst to N
destinations - N RxMsg instances are currently created.

Investigating generated data_msg.c code shows that neither Msg, nor TxMsg
have Py_TPFLAGS_HAVE_GC flag set, but RxMsg does have it set and does
have generated .tp_traverse and .tp_clear routines. Investigating a bit
more turns our that if we exclude `array.array burst` from RxMsg
definition, all those cyclic-GC related things go away from generated
code. So somehow Cython thinks that array.array can have a back pointer
to RxMsg and emits GC supporting code due to that.

But that is not possible to have a back-pointer from array.array to
RxMsg: the only object that array.array references is arraydescr object:

    https://github.com/cython/cython/blob/e22e99e9/Cython/Includes/cpython/array.pxd#L96-L102

which is plain C struct inside and does not reference other objects at all:

    https://github.com/cython/cython/blob/e22e99e9/Cython/Includes/cpython/array.pxd#L72-L76

-> So disable cyclic-GC support for RxMsg to avoid associated overhead.

Do so for TxMsg and Msg explicitly for symmetry as well.

Change-Id: I2c592cec4931db04c29cadfeb97ce5325295d862
---
M src/target/trx_toolkit/data_msg.pxd
M src/target/trx_toolkit/data_msg.pyx
2 files changed, 8 insertions(+), 2 deletions(-)

git pull ssh://gerrit.osmocom.org:29418/osmocom-bb refs/changes/85/40085/1

diff --git a/src/target/trx_toolkit/data_msg.pxd b/src/target/trx_toolkit/data_msg.pxd
index e0acbda..2eb6ed3 100644
--- a/src/target/trx_toolkit/data_msg.pxd
+++ b/src/target/trx_toolkit/data_msg.pxd
@@ -1,7 +1,7 @@
 # -*- coding: utf-8 -*-
 # cython: language_level=3
 
-from cython cimport final
+from cython cimport final, no_gc  # NOTE no_gc means "no cyclic gc", acyclic gc support is still there
 from cpython cimport array
 from libc.stdint cimport int8_t, int64_t, uint8_t
 
@@ -19,6 +19,7 @@
 cdef Modulation ModGMSK
 
 
+@no_gc
 cdef class Msg:
 	cdef readonly int      ver
 	cdef readonly int64_t  fn       # -1 if not valid
@@ -58,6 +59,7 @@
 
 
 @final
+@no_gc
 cdef class TxMsg(Msg):
 	cdef public bytearray burst  # | None
 	cdef readonly int pwr # -1 if unset
@@ -67,6 +69,7 @@
 
 
 @final
+@no_gc  # NOTE by default cython thinks that .burst might participate in cycle
 cdef class RxMsg(Msg):
 	cdef public array.array burst   # array.array[b] | None
 
diff --git a/src/target/trx_toolkit/data_msg.pyx b/src/target/trx_toolkit/data_msg.pyx
index 1e786c1..304dbdb 100644
--- a/src/target/trx_toolkit/data_msg.pyx
+++ b/src/target/trx_toolkit/data_msg.pyx
@@ -19,7 +19,7 @@
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 # GNU General Public License for more details.
 
-from cython cimport final
+from cython cimport final, no_gc
 from libc.stdint cimport int16_t, int64_t, uint16_t, uint32_t
 
 from cpython cimport array
@@ -79,6 +79,7 @@
 
 cdef int KNOWN_VERSION_MAX = 1  # 0, 1
 
+@no_gc
 cdef class Msg:
 	''' TRXD (DATA) message coding API (common part). '''
 
@@ -318,6 +319,7 @@
 cdef int PWR_MAX = 0xff
 
 @final
+@no_gc
 cdef class TxMsg(Msg):
 	''' Tx (L1 -> TRX) message coding API. '''
 
@@ -473,6 +475,7 @@
 
 
 @final
+@no_gc
 cdef class RxMsg(Msg):
 	''' Rx (TRX -> L1) message coding API. '''
 

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