Team C
[ZBX-11568] zbx_procstat_get_util() does not round up results correctly Created: 2016 Dec 07 Updated: 2024 Apr 10 Resolved: 2017 Mar 05 |
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| Status: | Closed |
| Project: | ZABBIX BUGS AND ISSUES |
| Component/s: | Agent (G) |
| Affects Version/s: | 3.0.4, 3.0.5 |
| Fix Version/s: | 3.0.8rc1, 3.2.4rc1, 3.4.0alpha1 |
| Type: | Incident report | Priority: | Trivial |
| Reporter: | Constantin Oshmyan | Assignee: | Unassigned |
| Resolution: | Fixed | Votes: | 0 |
| Labels: | agent | ||
| Remaining Estimate: | Not Specified | ||
| Time Spent: | Not Specified | ||
| Original Estimate: | Not Specified | ||
| Team: | Team C |
| Sprint: | Sprint 1, Sprint 2 |
| Story Points: | 1 |
| Description |
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The function zbx_procstat_get_util() in the file src/zabbix_agent/procstat.c calculates the CPU utilization. It gives the result as a percentage with accuracy 0.1% (type "double"). However, most calculations (probably, for optimization purpose) are with the integer types (variables ticks_diff and time_diff have type zbx_uint64_t). The final part of calculations is the following (lines 1102 – 1105): /* 1e9 (nanoseconds) * 1e2 (percent) * 1e1 (one digit decimal place) */ ticks_diff *= __UINT64_C(1000000000000); ticks_diff /= time_diff * sysconf(_SC_CLK_TCK); *value = (double)ticks_diff / 10; The main idea is, probably, used CPU time (in nanoseconds, multiplied to 1000) to divide by the elapsed time (in nanoseconds) to obtain the number of tens portion of percent before casting integer to double. If it is the intentional behaviour, this ticket could be closed safely. /* 1e9 (nanoseconds) * 1e2 (percent) * 1e2 (two digit decimal places for correct rounding up) */ ticks_diff *= __UINT64_C(10000000000000); <------ one zero longer ticks_diff /= time_diff * sysconf(_SC_CLK_TCK); /*correct rounding up */ ticks_diff += 5; ticks_diff /= 10; *value = (double)ticks_diff / 10; This part of code exists, at least, in versions 3.0.4, 3.0.5 and zabbix-3.0.6rc1. |
| Comments |
| Comment by Constantin Oshmyan [ 2016 Dec 07 ] |
...and just released v3.0.6 also. |
| Comment by Andrea Biscuola (Inactive) [ 2017 Feb 16 ] |
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Fixed in svn://svn.zabbix.com/branches/dev/ZBX-11568 Note: As there is no established rules regarding roundings, please if necessary provide additional info's regarding the test results (if the reported values are satisfactory or not). |
| Comment by Andris Zeila [ 2017 Feb 17 ] |
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(1) *value = round(ticks_diff / (time_diff * sysconf(_SC_CLK_TCK))) / 10; To fix it the ticks_diff should be forced to double value first
*value = round((double)ticks_diff / (time_diff * sysconf(_SC_CLK_TCK))) / 10;
abs Yes, completely forgot to add the explicit cast. RESOLVED in r65781 wiper CLOSED |
| Comment by Andris Zeila [ 2017 Feb 17 ] |
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Successfully tested |
| Comment by Andrea Biscuola (Inactive) [ 2017 Feb 17 ] |
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Fixed in r65790 for:
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| Comment by Alexander Vladishev [ 2017 Feb 17 ] |
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(2) [G] math.h already included in sysinc.h src/zabbix_agent/procstat.c @@ -17,6 +17,8 @@ ** Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. **/ +#include <math.h> + #include "common.h" #include "log.h" #include "mutexs.h" abs RESOLVED in r66032 (all the branches). Also as the issue was already tested, i think it can be safely closed sasha CLOSED |
| Comment by richlv [ 2017 Feb 20 ] |
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(3) the changelog entry currently says "fixed wrong number round for cpu statistics" - maybe something like "fixed incorrect number rounding for CPU statistics" would be slightly better abs FIXED in 66035 sasha CLOSED |
| Comment by Martins Valkovskis [ 2017 Mar 02 ] |