Created attachment 437669 [details] patch to check for overflow The customer is seeing occasionally strange values in sar reports for interrupt counts. 14:10:01 sum 1203.40 14:20:01 sum 1204.00 14:30:01 sum 30752774188809196.00 14:40:01 sum 1101.04 14:50:01 sum 1023.09 sar periodically gets the total number of interrupts from /proc/stat and calculates deltas for each point in time for this output. At the point where the strange sample occurs, one of the counters in /proc/stat went backwards. We've investigated a kernel fix for this and found it to be impossible without breaking kABI. Instead the customer and TAM propose simply detecting and redacting the strange samples in SAR output. 14:10:01 sum 1203.40 14:20:01 sum 1204.00 14:30:01 sum N/A 14:40:01 sum 1101.04 14:50:01 sum 1023.09 A patch to accomplish this is attached.
This request was evaluated by Red Hat Product Management for inclusion in the current release of Red Hat Enterprise Linux. Because the affected component is not scheduled to be updated in the current release, Red Hat is unfortunately unable to address this request at this time. Red Hat invites you to ask your support representative to propose this request, if appropriate and relevant, in the next release of Red Hat Enterprise Linux.
Technical note added. If any revisions are required, please edit the "Technical Notes" field accordingly. All revisions will be proofread by the Engineering Content Services team. New Contents: Previously, if kernel interrupt counters overflowed, the sar utility provided confusing output. This bug has been fixed and the sum of interrupts is now reported correctly.
An advisory has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on therefore solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHSA-2011-1005.html