To increase the shared memory segment size for multi-threaded data loaders, you can follow these steps:
1. Edit System Configuration:
- Become the superuser.
- Open the `/etc/system` file (on Solaris-based systems) or modify kernel parameters in `/proc/sys/kernel/shmmax` (on Linux systems).
- Add or modify variables to increase shared memory limits. For example, on Solaris:
bash
set shmsys:shminfo_shmmax=268435456
- This sets the maximum shared memory segment size to 256 MB. Adjust the value as needed.
2. Verify Changes:
- After saving the changes, verify that the shared memory values have been updated. On Linux, you can check the current `SHMMAX` value with:
bash
cat /proc/sys/kernel/shmmax
3. Reboot (if necessary):
- On some systems, you may need to reboot for the changes to take effect.
4. Use HugePages (Optional):
- For large memory requirements, consider using HugePages on Linux systems. This can improve performance by reducing page table overhead and ensuring that shared memory remains in RAM.
- Configure HugePages by setting the `hugepages` parameter based on your shared memory needs.
5. Implement Efficient Memory Management:
- Ensure your multi-threaded data loaders manage shared memory efficiently to avoid memory leaks or crashes. Use synchronization mechanisms to prevent concurrent access issues.
6. Handle Legacy Code Issues:
- If dealing with legacy code that crashes and leaves shared memory segments, use `shmctl` to delete and recreate segments as needed.
These steps should help you increase and manage shared memory effectively for your multi-threaded data loaders.
Citations:[1] https://docs.oracle.com/cd/E19455-01/805-7229/sysressysinfo-54361/index.html
[2] https://docs.oracle.com/cd/B28359_01/server.111/b32009/appi_vlm.htm
[3] https://docs.oracle.com/cd/E19504-01/802-5750/sysressysinfo-54361/index.html
[4] https://help.hcl-software.com/hclinformix/1410/admin/ids_admin_0431.html
[5] https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/5/html/tuning_and_optimizing_red_hat_enterprise_linux_for_oracle_9i_and_10g_databases/chap-oracle_9i_and_10g_tuning_guide-setting_shared_memory
[6] https://help.hcl-software.com/hclinformix/1410/adr/ids_sapi_008.html
[7] https://stackoverflow.com/questions/2261582/changing-existing-shared-memory-segment-size
[8] https://stackoverflow.com/questions/11909248/how-do-two-or-more-threads-share-memory-on-the-heap-that-they-have-allocated