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From: "agentzh at gmail dot com" <sourceware-bugzilla@sourceware.org>
To: systemtap@sourceware.org
Subject: [Bug runtime/31012] New: Bug: kernel module loading might block a
 CPU more than 1.5ms on very fast machines
Date: Mon, 30 Oct 2023 19:24:09 +0000
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X-Bugzilla-Product: systemtap
X-Bugzilla-Component: runtime
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X-Bugzilla-Who: agentzh at gmail dot com
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D31012

            Bug ID: 31012
           Summary: Bug: kernel module loading might block a CPU more than
                    1.5ms on very fast machines
           Product: systemtap
           Version: unspecified
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: runtime
          Assignee: systemtap at sourceware dot org
          Reporter: agentzh at gmail dot com
  Target Milestone: ---

Currently, the module init code calls the expensive kernel function
kallsyms_lookup_name() several times, which would block a CPU core for more
than 1.5ms on high-speed machines (Core i9-13900K).

Each kallsyms_lookup_name() might take more than 800us here.

We should add cond_resched() calls to mitigate this blocking effect. Will
prepare a patch shortly.

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