loci: use minimal allocation for fixed-length objects
Previously we allocated the full 64KB even for objects like the barrier reply,
which will only ever use 8 bytes. Allocating and zeroing unnecessarily large
wire buffers was a performance problem.
This change increases performance in my barrier microbenchmark by 46%.
diff --git a/c_gen/c_code_gen.py b/c_gen/c_code_gen.py
index 81f5a1a..ed923cb 100644
--- a/c_gen/c_code_gen.py
+++ b/c_gen/c_code_gen.py
@@ -2146,6 +2146,10 @@
if not type_maps.class_is_virtual(cls):
gen_wire_push_fn(cls, out)
+ uclass = loxi_globals.unified.class_by_name(cls)
+ is_fixed_length = uclass and uclass.is_fixed_length
+ max_length = is_fixed_length and "bytes" or "OF_WIRE_BUFFER_MAX_LENGTH"
+
out.write("""
/**
* Create a new %(cls)s object
@@ -2170,13 +2174,12 @@
bytes = of_object_fixed_len[version][%(enum)s] + of_object_extra_len[version][%(enum)s];
- /* Allocate a maximum-length wire buffer assuming we'll be appending to it. */
- if ((obj = (%(cls)s_t *)of_object_new(OF_WIRE_BUFFER_MAX_LENGTH)) == NULL) {
+ if ((obj = (%(cls)s_t *)of_object_new(%(max_length)s)) == NULL) {
return NULL;
}
%(cls)s_init(obj, version, bytes, 0);
-""" % dict(cls=cls, enum=enum_name(cls)))
+""" % dict(cls=cls, enum=enum_name(cls), max_length=max_length))
if not type_maps.class_is_virtual(cls):
out.write("""
if (%(cls)s_push_wire_values(obj) < 0) {