| Title | eventcnv appears to hang if you specify a small bucket size |
| Status | closed |
| Priority | optional |
| Assigned user | Gareth Rees |
| Organization | Ravenbrook |
| Description | The eventcnv program takes a -b command-line argument that specifies a "bucket size": the time granularity with which statistics are reported. If you specify a small bucket size (say, "-b 1000" or less), eventcnv appears to hang, with no output appearing for many seconds. This behaviour is confusing for a new user (who might not understand the units for the -b option) and hard to explain in the documentation. |
| Analysis | There should be no reason why eventcnv should take any longer when a bucket size is specified (other than the small amount of extra time needed to output the extra rows of stats for each populated bucket). The offending code is this in eventcnv.c: /* Output bucket, if necessary, and update counters */ if (bucketSize != 0 && eventTime >= bucketLimit) { reportBucketResults(bucketLimit-1); clearBucket(); do { bucketLimit += bucketSize; } while (eventTime >= bucketLimit); } The do loop should be replaced with something like bucketLimit = ((eventTime / BucketLimit) + 1) * bucketLimit; See also job003332, job003333, and job003335, which also affect this region of code. |
| How found | manual_test |
| Evidence | On a small telemetry log (just 483 events) I got the following timings: $ time $EVENTCNV -e all > /dev/null real 0m0.005s $ time $EVENTCNV -e all -b 1000000 > /dev/null real 0m0.010s $ time $EVENTCNV -e all -b 100000 > /dev/null real 0m0.042s $ time $EVENTCNV -e all -b 10000 > /dev/null real 0m0.368s $ time $EVENTCNV -e all -b 1000 > /dev/null real 0m3.624s $ time $EVENTCNV -e all -b 100 > /dev/null real 0m36.194s I didn't try it, but it looks as though the time taken is inversely proportional to the bucket size, and so "-b 1" would take an hour. |
| Observed in | 1.110.0 |
| Created by | Gareth Rees |
| Created on | 2012-10-21 15:34:03 |
| Last modified by | Gareth Rees |
| Last modified on | 2012-10-23 14:28:22 |
| History | 2012-10-21 GDR Created. |
| Change | Effect | Date | User | Description |
|---|---|---|---|---|
| 180028 | closed | 2012-10-23 14:28:22 | Gareth Rees | Remove reporting features from eventcnv, as discussed with RB. Eventcnv was always intended to be a simple tool that just translates events, not a report generator. In particular: * Remove -e option and associated event specification parsing. * Remove -b option and bucket statistics. * Don't intern labels (always print addresses). * Remove -v option (events are always output). * If -h or -? is specified, exit after printing help message. * Help text refer to the "Telemetry" section of reference manual. |