scripts/trace: create trace provider abstraction

This abstraction will make it possible to support different sources for
the traces.  The current JSON implementation is moved to a provdider and
a new one using the trace_parse library will be added in the following
patches.

Signed-off-by: Konrad Sztyber <konrad.sztyber@intel.com>
Change-Id: I322e7984ffe19ce8b8e1bb551e8339655383623f
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/9437
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Community-CI: Broadcom CI <spdk-ci.pdl@broadcom.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Krzysztof Karas <krzysztof.karas@intel.com>
Reviewed-by: Aleksey Marchuk <alexeymar@mellanox.com>

scripts/bpf/trace.py

@@ -165,19 +165,33 @@ class TraceEntry:
     args: Dict[str, TypeVar('ArgumentType', str, int)]
 
 
-class Trace:
-    """Stores, parses, and prints out SPDK traces"""
+class TraceProvider:
+    """Defines interface for objects providing traces and tracepoint definitions"""
+
+    def tpoints(self):
+        """Returns tracepoint definitions as a dict of (tracepoint_name, tracepoint)"""
+        raise NotImplementedError()
+
+    def entries(self):
+        """Generator returning subsequent trace entries"""
+        raise NotImplementedError()
+
+    def tsc_rate(self):
+        """Returns the TSC rate that was in place when traces were collected"""
+        raise NotImplementedError()
+
+
+class JsonProvider(TraceProvider):
+    """Trace provider based on JSON-formatted output produced by spdk_trace app"""
     def __init__(self, file):
         self._parser = ijson.parse(file)
-        self._objects = []
-        self._argfmt = {TracepointArgument.TYPE_PTR: lambda a: f'0x{a:x}'}
-        self.tpoints = {}
+        self._tpoints = {}
         self._parse_defs()
 
     def _parse_tpoints(self, tpoints):
         for tpoint in tpoints:
             tpoint_id = tpoint['id']
-            self.tpoints[tpoint_id] = Tracepoint(
+            self._tpoints[tpoint_id] = Tracepoint(
                 name=tpoint['name'], id=tpoint_id,
                 new_object=tpoint['new_object'],
                 args=[TracepointArgument(name=a['name'],
@@ -191,7 +205,7 @@ class Trace:
             if prefix == 'entries':
                 break
             elif prefix == 'tsc_rate':
-                self.tsc_rate = value
+                self._tsc_rate = value
                 continue
 
             if (prefix, event) == ('tpoints', 'start_array'):
@@ -203,7 +217,7 @@ class Trace:
                 builder = None
 
     def _parse_entry(self, entry):
-        tpoint = self.tpoints[entry['tpoint']]
+        tpoint = self._tpoints[entry['tpoint']]
         obj = entry.get('object', {})
         return TraceEntry(tpoint=tpoint, lcore=entry['lcore'], tsc=entry['tsc'],
                           size=entry.get('size'), object_id=obj.get('id'),
@@ -211,7 +225,13 @@ class Trace:
                           poller=entry.get('poller'),
                           args={n.name: v for n, v in zip(tpoint.args, entry.get('args', []))})
 
-    def _entries(self):
+    def tsc_rate(self):
+        return self._tsc_rate
+
+    def tpoints(self):
+        return self._tpoints
+
+    def entries(self):
         builder = None
         for prefix, event, value in self._parser:
             if (prefix, event) == ('entries.item', 'start_map'):
@@ -222,6 +242,15 @@ class Trace:
                 yield self._parse_entry(builder.value)
                 builder = None
 
+
+class Trace:
+    """Stores, parses, and prints out SPDK traces"""
+    def __init__(self, file):
+        self._provider = JsonProvider(file)
+        self._objects = []
+        self._argfmt = {TracepointArgument.TYPE_PTR: lambda a: f'0x{a:x}'}
+        self.tpoints = self._provider.tpoints()
+
     def _annotate_args(self, entry):
         annotations = {}
         for obj in self._objects:
@@ -248,10 +277,10 @@ class Trace:
 
     def print(self):
         def get_us(tsc, off):
-            return ((tsc - off) * 10 ** 6) / self.tsc_rate
+            return ((tsc - off) * 10 ** 6) / self._provider.tsc_rate()
 
         offset = None
-        for e in self._entries():
+        for e in self._provider.entries():
             offset = e.tsc if offset is None else offset
             timestamp = get_us(e.tsc, offset)
             diff = get_us(e.time, 0) if e.time is not None else None