Huge latency on pselect

 If you're experiencing high latency on the `pselect` system call in your code, it can be caused by several factors. `pselect` is used for waiting on multiple file descriptors and can be affected by various conditions. Here are some potential reasons and solutions for latency issues with `pselect`:


1. **Blocking Operations on File Descriptors:**

   If any of the file descriptors you're monitoring with `pselect` block for a long time (e.g., due to slow I/O operations), it can introduce latency. Ensure that the file descriptors you're waiting on are not causing the delay.


2. **Signal Handling:**

   The `pselect` system call can be interrupted by signals. If you have signal handlers that execute slowly or frequently, it can lead to latency. Review your signal handling code to optimize it or reduce the frequency of signal delivery.


3. **Resource Contention:**

   System-wide resource contention, such as CPU or memory contention, can cause latency in all system calls, including `pselect`. Check system resource usage and consider optimizing your system configuration.


4. **Thread or Process Priority:**

   If your process or thread has low priority, it may experience higher latency. Consider adjusting the process/thread priority if it's appropriate for your application.


5. **Large Number of File Descriptors:**

   Managing a large number of file descriptors in a single `pselect` call can lead to increased latency. You may want to reconsider your design and whether it's possible to reduce the number of monitored file descriptors or split them across multiple `pselect` calls.


6. **Use Non-blocking I/O:**

   Consider using non-blocking I/O or asynchronous I/O to avoid blocking on file descriptors, especially if the latency is due to I/O operations.


7. **Monitor for Errors:**

   Ensure that you're monitoring for errors when using `pselect`. If an error occurs, you should handle it promptly to prevent latency from accumulating.


8. **Monitor for EINTR:**

   Be aware that `pselect` can be interrupted by signals, which can lead to `EINTR` (interrupted system call). You should handle this error appropriately in your code.


9. **Profile and Benchmark:**

   Use profiling tools to identify the specific source of latency in your application. Benchmarks and profiling can help pinpoint performance bottlenecks.


10. **Thoroughly Review Your Code:**

    Carefully review your code, looking for any unnecessary delays, suboptimal algorithms, or inefficient I/O operations that may contribute to latency.


If you're still experiencing latency after examining these potential issues, consider providing more details about your use case or the specific conditions where you're observing high latency. This information can help in providing more targeted advice for your situation.

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