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<a href="https://gitlab.rtems.org/wmthornton-dev">Wayne Thornton</a> created an issue: <a href="https://gitlab.rtems.org/rtems/rtos/rtems/-/issues/5582">#5582</a>
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Assignee: Wayne Thornton
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<h2 id="user-content-summary" dir="auto" style="margin-top: 0; margin-bottom: 10px;" align="initial">Summary<a href="#summary" aria-label="Link to heading 'Summary'" data-heading-content="Summary" class="anchor" style="margin-top: 0;"></a>
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<p dir="auto" style="color: #3a383f; margin: 0 0 1rem;" align="initial">In response to <a href="https://gitlab.rtems.org/chris" title="Chris Johns" class="gfm gfm-project_member js-user-link" data-user="3" data-original="@chris" data-container="body" data-placement="top" data-reference-type="user" style="color: #284779; background-color: #cbe2f9; border-radius: .25rem; margin-top: 0; padding: 0 2px;">@chris</a> comment (<a href="https://gitlab.rtems.org/rtems/rtos/rtems/-/merge_requests/1193#note_150641" title="cpukit: Create DHRL Library for DRAM Latency Mitigation" class="gfm gfm-merge_request" data-original="https://gitlab.rtems.org/rtems/rtos/rtems/-/merge_requests/1193#note_150641" data-link="false" data-link-reference="true" data-merge-request="2511" data-project="26" data-project-path="rtems/rtos/rtems" data-iid="1193" data-container="body" data-placement="top" data-reference-type="merge_request">!1193 (comment 150641)</a>) on my DHRL Merge Request (<a href="https://gitlab.rtems.org/rtems/rtos/rtems/-/merge_requests/1193" title="cpukit: Create DHRL Library for DRAM Latency Mitigation" class="gfm gfm-merge_request" data-original="https://gitlab.rtems.org/rtems/rtos/rtems/-/merge_requests/1193" data-link="false" data-link-reference="true" data-merge-request="2511" data-project="26" data-project-path="rtems/rtos/rtems" data-iid="1193" data-container="body" data-placement="top" data-reference-type="merge_request">!1193</a>) I will be looking at adding a barrier API to the self-contained API set in <code style="font-size: 90%; color: #18171d; word-wrap: break-word; background-color: #ececef; border-radius: .25rem; font-weight: inherit; overflow-wrap: break-word; white-space: break-spaces; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: keep-all; padding: 0.125rem 0.25rem;">cpukit/include/rtems/thread.h</code></p>
<p dir="auto" style="color: #3a383f; margin: 0 0 1rem;" align="initial">Every time the DHRL fast-path execution loop calls <code style="font-size: 90%; color: #18171d; word-wrap: break-word; background-color: #ececef; border-radius: .25rem; margin-top: 0; font-weight: inherit; overflow-wrap: break-word; white-space: break-spaces; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: keep-all; padding: 0.125rem 0.25rem;">rtems_barrier_wait()</code>, the OS has to disable interrupts, look up that ID in the Object Manager's internal tables, validate it, and then execute the barrier logic. By embedding the barrier directly into the <code style="font-size: 90%; color: #18171d; word-wrap: break-word; background-color: #ececef; border-radius: .25rem; font-weight: inherit; overflow-wrap: break-word; white-space: break-spaces; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: keep-all; padding: 0.125rem 0.25rem;">rtems_dhrl_control</code> structure, we can interact directly with the memory address. There is zero ID lookup latency, making it beneficial for performance-critical subsystems.</p>
<p dir="auto" style="color: #3a383f; margin: 0 0 1rem;" align="initial">By implementing this, there will be a secondary benefit: we no longer need the <code style="font-size: 90%; color: #18171d; word-wrap: break-word; background-color: #ececef; border-radius: .25rem; margin-top: 0; font-weight: inherit; overflow-wrap: break-word; white-space: break-spaces; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: keep-all; padding: 0.125rem 0.25rem;">RTEMS_DHRL_BARRIERS_PER_INSTANCE</code> configuration macro in <code style="font-size: 90%; color: #18171d; word-wrap: break-word; background-color: #ececef; border-radius: .25rem; font-weight: inherit; overflow-wrap: break-word; white-space: break-spaces; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: keep-all; padding: 0.125rem 0.25rem;">dhrl.h</code>, as self-contained objects don't consume global Workspace resources.</p>
<h2 id="user-content-steps-to-reproduce" dir="auto" style="margin-top: 20px; margin-bottom: 0;" align="initial">Steps to reproduce<a href="#steps-to-reproduce" aria-label="Link to heading 'Steps to reproduce'" data-heading-content="Steps to reproduce" class="anchor" style="margin-top: 0;"></a>
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