Merge pull request iovisor#861 from brendangregg/master

Improve linear histogram limit, and improve error message.

src/python/bcc/table.py

@@ -33,6 +33,8 @@
 BPF_MAP_TYPE_LRU_PERCPU_HASH = 10
 
 stars_max = 40
+log2_index_max = 65
+linear_index_max = 1025
 
 # helper functions, consider moving these to a utils module
 def _stars(val, val_max, width):
@@ -287,6 +289,8 @@ def print_log2_hist(self, val_type="value", section_header="Bucket ptr",
  If section_print_fn is not None, it will be passed the bucket value
  to format into a string as it sees fit. If bucket_fn is not None,
  it will be used to produce a bucket value for the histogram keys.
+ The maximum index allowed is log2_index_max (65), which will
+ accomodate any 64-bit integer in the histogram.
  """
  if isinstance(self.Key(), ct.Structure):
  tmp = {}
@@ -296,7 +300,7 @@ def print_log2_hist(self, val_type="value", section_header="Bucket ptr",
  bucket = getattr(k, f1)
  if bucket_fn:
  bucket = bucket_fn(bucket)
- vals = tmp[bucket] = tmp.get(bucket, [0] * 65)
+ vals = tmp[bucket] = tmp.get(bucket, [0] * log2_index_max)
  slot = getattr(k, f2)
  vals[slot] = v.value
  for bucket, vals in tmp.items():
@@ -307,7 +311,7 @@ def print_log2_hist(self, val_type="value", section_header="Bucket ptr",
  print("\n%s = %r" % (section_header, bucket))
  _print_log2_hist(vals, val_type)
  else:
- vals = [0] * 65
+ vals = [0] * log2_index_max
  for k, v in self.items():
  vals[k.value] = v.value
  _print_log2_hist(vals, val_type)
@@ -318,12 +322,14 @@ def print_linear_hist(self, val_type="value", section_header="Bucket ptr",
  section_print_fn=None, bucket_fn=None)
 
  Prints a table as a linear histogram. This is intended to span integer
- ranges, eg, from 0 to 100. The val_type argument is optional, and is a
- column header. If the histogram has a secondary key, multiple tables
- will print and section_header can be used as a header description for
- each. If section_print_fn is not None, it will be passed the bucket
- value to format into a string as it sees fit. If bucket_fn is not None,
+ ranges, eg, from 0 to 100. The val_type argument is optional, and is a
+ column header. If the histogram has a secondary key, multiple tables
+ will print and section_header can be used as a header description for
+ each. If section_print_fn is not None, it will be passed the bucket
+ value to format into a string as it sees fit. If bucket_fn is not None,
  it will be used to produce a bucket value for the histogram keys.
+ The maximum index allowed is linear_index_max (1025), which is hoped
+ to be sufficient for integer ranges spanned.
  """
  if isinstance(self.Key(), ct.Structure):
  tmp = {}
@@ -333,7 +339,7 @@ def print_linear_hist(self, val_type="value", section_header="Bucket ptr",
  bucket = getattr(k, f1)
  if bucket_fn:
  bucket = bucket_fn(bucket)
- vals = tmp[bucket] = tmp.get(bucket, [0] * 65)
+ vals = tmp[bucket] = tmp.get(bucket, [0] * linear_index_max)
  slot = getattr(k, f2)
  vals[slot] = v.value
  for bucket, vals in tmp.items():
@@ -344,9 +350,15 @@ def print_linear_hist(self, val_type="value", section_header="Bucket ptr",
  print("\n%s = %r" % (section_header, bucket))
  _print_linear_hist(vals, val_type)
  else:
- vals = [0] * 65
+ vals = [0] * linear_index_max
  for k, v in self.items():
- vals[k.value] = v.value
+ try:
+ vals[k.value] = v.value
+ except IndexError:
+ # Improve error text. If the limit proves a nusiance, this
+ # function be rewritten to avoid having one.
+ raise IndexError(("Index in print_linear_hist() of %d " +
+ "exceeds max of %d.") % (k.value, linear_index_max))
  _print_linear_hist(vals, val_type)