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Delphi memory allocators and configuration notes in multi-threaded environments with high allocation/deallocation rates

Posted by jpluimers on 2020/02/20

From an interesting discussion at [Archive.is/WayBack] FaceBook: Delphi developer thread by Jarto Tarpio with some measurements by Jarto Tarpio and André Mussche.

  • Manipulation of strings and lists in Delphi have high memory allocation/deallocation rates, so HTTP related services with high call rates are affected more than regular services
  •  FastMM:
    • conditional defines that can help are NeverSleepOnThreadContention, UseSwitchToThread, and UseReleaseStack then measure.
    • has one huge advantage: It’s very, very good at keeping memory fragmentation at bay
    • default settings are for applications that use lots of CPU, but have no really high memory allocation/deallocation rates
    • has very good debugging facilities
    • Under FullDebugMode address space is never released back to the operating system so once the address space has been exhausted there is very little room to manoeuvre.
  • TCMalloc:
    • is very good at multi-threaded memory management with high allocation/deallocation rates
    • needs to be persuaded to releases memory to the OS:
      it only releases to the system under two occasions: Freeing another part of the memory, or asking it to release all parts marked as freed.

    • has no debugging facilities

The differences make it a challenge to integrate in your development and deployment process: because of the debugging facilities, you’d like FastMM in all your environments, but TCMalloc in multi-threaded environments with high allocation/deallocation rates.

One possibility is to have your CI environment deliver both in all stages, run all tests on both, then choose the final one depending on your run-time configuration.

That gives a burden on configuring your Continuous Integration, but the gain might outweigh this cost.

Relevant links from the Facebook thread:

–jeroen

5 Responses to “Delphi memory allocators and configuration notes in multi-threaded environments with high allocation/deallocation rates”

  1. Roberto Della Pasqua said

    Will update it soon with a pair of bugs correction

  2. https://github.com/RDP1974 Intel libraries are better than google performance, more reliable and fast, take a look

  3. I did a lot of research on a dozen of mem allocators, and found the Intel TBB (free license) to be the most fast, reliable and less prone to fragmentation for multithreaded apps.
    Feel free to check https://github.com/RDP1974/Sea-Delphi-RTL-IIS-Filter with pascal wrappers over the libraries.

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