5.12 merge window, part 2 [LWN.net]

5.12 merge window, part 2

Posted Mar 2, 2021 12:20 UTC (Tue) by karkhaz (subscriber, #99844)
Parent article: 5.12 merge window, part 2

> A new memory-debugging tool called "kfence" has been merged; it can find a number of types of errors (use-after-free, buffer overflow, etc.) and features a low-enough overhead to, it seems, be usable on production systems. See this documentation commit for more information.

Cool, looking forward to trying this out! This seems like a fairly low-effort way for testing new stable kernels before deploying them---compile the kernel with KFENCE and run various workloads on a test machine for some days, perhaps with KFENCE_NUM_OBJECTS and KFENCE_SAMPLE_INTERVAL set to much higher values to be able to show bugs up more quickly.

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5.12 merge window, part 2

Posted Mar 2, 2021 17:58 UTC (Tue) by melver (subscriber, #134990) [Link]

While KFENCE was designed to be deployed at scale and for our use-cases are looking at KFENCE_SAMPLE_INTERVAL >= 500 milliseconds, I'm also aware of a KFENCE deployment where they chose KFENCE_SAMPLE_INTERVAL=1 ms (and lower with experimental patches) and very large KFENCE_NUM_OBJECTS (65535 -> 512 MiB) and found bugs that way. For such aggressive configs, see what performance you get, but my guess is that at sample intervals as low as 1 ms, you'll want to switch to KFENCE's non-static-branch mode with CONFIG_KFENCE_STATIC_KEYS=n.