prevent invalid compression ratio values

diff --git a/src/plugin_proc.c b/src/plugin_proc.c
index ffcc32c44a0875b928edf0118bf090026bd112b5..0e2d9c1227018b513317f009fe64677fd104f905 100644 (file)
--- a/src/plugin_proc.c
+++ b/src/plugin_proc.c
@@ -351,17 +351,19 @@ void *proc_main(void *ptr)
                        }
                        else rrdset_next(stcompression);
 
-                       unsigned long long gcontent_size            = global_statistics.content_size;
+                       // since we don't lock here to read the global statistics
+                       // read the smaller value first
                        unsigned long long gcompressed_content_size = global_statistics.compressed_content_size;
+                       unsigned long long gcontent_size            = global_statistics.content_size;
 
-                       unsigned long long content_size             = gcontent_size            - old_content_size;
                        unsigned long long compressed_content_size  = gcompressed_content_size - old_compressed_content_size;
+                       unsigned long long content_size             = gcontent_size            - old_content_size;
 
-                       old_content_size            = gcontent_size;
                        old_compressed_content_size = gcompressed_content_size;
+                       old_content_size            = gcontent_size;
 
-                       if(content_size)
-                               compression_ratio = (content_size - compressed_content_size) * 100 * 1000 / content_size;
+                       if(content_size && content_size >= compressed_content_size)
+                               compression_ratio = ((content_size - compressed_content_size) * 100 * 1000) / content_size;
 
                        if(compression_ratio != -1)
                                rrddim_set(stcompression, "savings", compression_ratio);