diff --git a/riscv-isac/riscv_isac/cgf_normalize.py b/riscv-isac/riscv_isac/cgf_normalize.py
index 7202adb56..a1c71d968 100644
--- a/riscv-isac/riscv_isac/cgf_normalize.py
+++ b/riscv-isac/riscv_isac/cgf_normalize.py
@@ -580,10 +580,10 @@ def expand_cgf(cgf_files, xlen,flen, log_redundant=False):
                     if len(cgf[labels]['mnemonics'].keys()) > 1:
                         logger.error(f'Multiple instruction mnemonics found when base_op label defined in {labels} label.')
 
-            # Substitute instruction aliases with equivalent tuple of instructions   
+            # Substitute instruction aliases with equivalent tuple of instructions
             if 'cross_comb' in cats:
                 temp = cats['cross_comb']
-                
+
                 for covp, covge in dict(temp).items():
                     data = covp.split('::')
                     ops = data[0].replace(' ', '')[1:-1].split(':')
@@ -592,14 +592,14 @@ def expand_cgf(cgf_files, xlen,flen, log_redundant=False):
                         exp_alias = utils.import_instr_alias(ops[i])
                         if exp_alias != None:
                             ops[i] = tuple(exp_alias).__str__().replace("'", '').replace(" ", '')
-                    
+
                     data[0] = '[' + ':'.join(ops) + ']'
                     data = '::'.join(data)
                     del temp[covp]
                     temp[data] = covge
-                
-                cgf[labels].insert(1, 'cross_comb', temp)                 
-            
+
+                cgf[labels].insert(1, 'cross_comb', temp)
+
             l = len(cats.items())
             i = 0
             for label,node in cats.items():
@@ -618,7 +618,13 @@ def expand_cgf(cgf_files, xlen,flen, log_redundant=False):
                                 for cp,comment in exp_cp:
                                     if log_redundant and cp in cgf[labels][label]:
                                         logger.warn(f'Redundant coverpoint during normalization: {cp}')
-                                    cgf[labels][label].insert(l+i,cp,coverage,comment=comment)
+
+                                    # PyYAML has catastrophic performance adding comments
+                                    # so only do it for the first 100 entries.
+                                    if i < 100:
+                                        cgf[labels][label].yaml_add_eol_comment(comment, key=cp)
+                                    else:
+                                        cgf[labels][label][cp] = coverage
+
                                     i += 1
     return dict(cgf)
-