Use CLOCK_MONOTONIC_RAW instead of CLOCK_MONOTONIC#5099
Use CLOCK_MONOTONIC_RAW instead of CLOCK_MONOTONIC#5099renecannao merged 2 commits intosysown:v3.0from
CLOCK_MONOTONIC_RAW instead of CLOCK_MONOTONIC#5099Conversation
Signed-off-by: Wazir Ahmed <wazir@proxysql.com>
…t_time` Signed-off-by: Wazir Ahmed <wazir@proxysql.com>
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Summary of Changes
Hello @wazir-ahmed, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!
This pull request refines the system's timekeeping mechanisms to enhance the reliability and precision of performance metrics, particularly for query execution times. It achieves this by adopting a more robust clock source and implementing safeguards to prevent logical errors in time interval calculations.
Highlights
- Improved Time Measurement Accuracy: The system now prioritizes
CLOCK_MONOTONIC_RAWfor time measurements, falling back toCLOCK_MONOTONICifRAWis unavailable. This ensures more stable and accurate elapsed time calculations, asCLOCK_MONOTONIC_RAWis not subject to system time adjustments like NTP. - Ensured Query Time Consistency: New
set_end_timemethods have been introduced forQuery_Info(MySQL) andPgSQL_Query_Info(PostgreSQL) to guarantee that a query'send_timeis always greater than or equal to itsstart_time. This addresses potential inconsistencies in query duration tracking. - Standardized Clock Usage: A new macro,
PROXYSQL_CLOCK_MONOTONIC, has been defined and applied across the codebase to centralize the choice betweenCLOCK_MONOTONIC_RAWandCLOCK_MONOTONIC, promoting consistency and maintainability in time-related operations.
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Code Review
This pull request correctly implements the switch to CLOCK_MONOTONIC_RAW when available, which is a good improvement for time measurements as it's not affected by NTP adjustments. The fallback logic to ensure end_time is always greater than or equal to start_time is also a solid addition for robustness.
My review focuses on improving maintainability by addressing some code duplication. I've identified two instances of duplicated logic that could be refactored into shared components. These changes will make the codebase cleaner and easier to maintain in the long run.
| inline void Query_Info::set_end_time(unsigned long long time) { | ||
| end_time = time; | ||
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| #ifndef CLOCK_MONOTONIC_RAW | ||
| if (start_time <= end_time) | ||
| return; | ||
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| // If start_time is greater than end_time, assign current monotonic time | ||
| end_time = monotonic_time(); | ||
| if (start_time <= end_time) | ||
| return; | ||
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| // If start_time is still greater than end_time, set the difference to 0 | ||
| end_time = start_time; | ||
| #endif // CLOCK_MONOTONIC_RAW | ||
| } |
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The implementation of set_end_time is identical to the one in PgSQL_Query_Info::set_end_time. To improve maintainability and avoid code duplication, this logic should be extracted into a shared helper function. For example, you could create a helper function in gen_utils.h and call it from both methods.
| inline void PgSQL_Query_Info::set_end_time(unsigned long long time) { | ||
| end_time = time; | ||
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| #ifndef CLOCK_MONOTONIC_RAW | ||
| if (start_time <= end_time) | ||
| return; | ||
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| // If start_time is greater than end_time, assign current monotonic time | ||
| end_time = monotonic_time(); | ||
| if (start_time <= end_time) | ||
| return; | ||
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| // If start_time is still greater than end_time, set the difference to 0 | ||
| end_time = start_time; | ||
| #endif // CLOCK_MONOTONIC_RAW | ||
| } |
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The implementation of set_end_time is duplicated in Query_Info::set_end_time. To improve maintainability and avoid code duplication, this logic should be extracted into a shared helper function. For example, you could create a helper function in gen_utils.h and call it from both methods.
| #ifdef CLOCK_MONOTONIC_RAW | ||
| #define PROXYSQL_CLOCK_MONOTONIC CLOCK_MONOTONIC_RAW | ||
| #else | ||
| #define PROXYSQL_CLOCK_MONOTONIC CLOCK_MONOTONIC | ||
| #endif |
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The definition of PROXYSQL_CLOCK_MONOTONIC is duplicated from include/gen_utils.h. To avoid this duplication, consider moving this macro to a more specific, shared header file that can be included by both gen_utils.h and this file. Alternatively, if dependencies allow, test/tap/tap/utils.h could include include/gen_utils.h directly.
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CLOCK_MONOTONIC_RAWwhen available and fallback toCLOCK_MONOTONICQueryInfo::end_timeis always be greater than or equal tostart_time.Closes #4950.