Davidlohr Bueso davidlohr
davidlohr
/ io_uring_profile.bt
Created
April 23, 2026 20:03
BPF script to profile io_uring workloads
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| #!/usr/bin/env bpftrace | |
| /* | |
| * io_uring workload insight. | |
| * | |
| * Gives a complete picture of io_uring activity during a workload: | |
| * - ring lifecycle (create, cqring wait) | |
| * - submission & completion volume and per-opcode breakdown | |
| * - per-request latency (submit -> complete) per opcode | |
| * - registration-path activity (buffers/files/etc.), with stacks | |
| * - async-work offload and io_uring_enter traffic |
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| #!/usr/bin/env bpftrace | |
| /* | |
| * hmm-snoop.bt -- comprehensive observer for Linux HMM / CPU-GPU memory | |
| * | |
| * Reports all CPU<->device memory interactions that flow through the | |
| * kernel's HMM (Heterogeneous Memory Management) APIs, without any driver | |
| * cooperation. Works transparently for any driver that uses the standard | |
| * migrate_vma_* / hmm_range_fault interface: amdgpu/amdkfd, nouveau, | |
| * drm/xe (via drm_pagemap), and lib/test_hmm. No kernel patches required. | |
| * |
davidlohr
/ offline_mem.sh
Last active
October 4, 2025 19:05
A script to offline a certain percentage of memory from a specific NUMA node.
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| #!/bin/bash | |
| # A script to offline a certain percentage of memory from a specific NUMA node. | |
| # --- Input Validation --- | |
| if [ "$EUID" -ne 0 ]; then | |
| echo "Please run as root." | |
| exit 1 | |
| fi |
davidlohr
/ extfragsnoop.bt
Last active
May 13, 2025 01:32
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| #!/usr/bin/env bpftrace | |
| /* | |
| * extfragsnoop Trace events that induce system external memory fragmentation. | |
| * For Linux, uses bpftrace and eBPF. | |
| * | |
| * This traces when a fallback event occurs, particularly mixed pageblocks that | |
| * occur as a consequence of pollution upon memory pressure. | |
| * | |
| * Unmovable memory is the enemy of a de-fragmenting process (compaction), so | |
| * gather such allocations as well as situations when movable memory becomes |
davidlohr
/ qemu-4xinterleave-switch-type3.cfg
Last active
December 11, 2023 02:09
syzkaller config - qemu deployment emulating a 4 devices setup below a switch suitable for 1, 2 or 4 way interleave
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| { | |
| "target": "linux/amd64", | |
| "http": "127.0.0.1:56741", | |
| "workdir": "workdir", | |
| "kernel_obj": "/home/dave/code/linux/", | |
| "image": "/img/bullseye.img", | |
| "sshkey": "/img/bullseye.id_rsa", | |
| "syzkaller": "/home/dave/code/syzkaller", | |
| "procs": 8, | |
| "type": "qemu", |
davidlohr
/ qemu-4xinterleave-1cfmw-2hb-2rp-type3.cfg
Last active
December 24, 2024 16:06
syzkaller config - qemu deployment emulating a setup suitable for 4 way interleave. Only one fixed window provided, to enable 2 way interleave across 2 CXL host bridges. Each host bridge has 2 CXL Root Ports, with the CXL Type3 device directly attached (no switches).
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| { | |
| "target": "linux/amd64", | |
| "http": "127.0.0.1:56741", | |
| "workdir": "workdir", | |
| "kernel_obj": "/home/dave/code/linux/", | |
| "image": "/img/bullseye.img", | |
| "sshkey": "/img/bullseye.id_rsa", | |
| "syzkaller": "/home/dave/code/syzkaller", | |
| "procs": 8, | |
| "type": "qemu", |
davidlohr
/ qemu-single-volatile-nolsa-type3.cfg
Last active
December 11, 2023 02:11
syzkaller config - qemu deployment emulating a simple setup with just one directly attached CXL Type 3 volatile memory device
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| { | |
| "target": "linux/amd64", | |
| "http": "127.0.0.1:56741", | |
| "workdir": "workdir", | |
| "kernel_obj": "/home/dave/code/linux/", | |
| "image": "/img/bullseye.img", | |
| "sshkey": "/img/bullseye.id_rsa", | |
| "syzkaller": "/home/dave/code/syzkaller", | |
| "procs": 8, | |
| "type": "qemu", |
davidlohr
/ qemu-single-pmem-type3.cfg
Last active
December 11, 2023 02:09
syzkaller config - qemu deployment emulating a simple setup with just one directly attached CXL Type 3 Persistent Memory device
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| { | |
| "target": "linux/amd64", | |
| "http": "127.0.0.1:56741", | |
| "workdir": "workdir", | |
| "kernel_obj": "/home/dave/code/linux/", | |
| "image": "/img/bullseye.img", | |
| "sshkey": "/img/bullseye.id_rsa", | |
| "syzkaller": "/home/dave/code/syzkaller", | |
| "procs": 8, | |
| "type": "qemu", |
davidlohr
/ kernel callgraph visual
Created
June 9, 2022 18:50
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| Applies to the MM, but works on any subsystem. | |
| Based on https://deferred.io/2015/10/27/visualizing-linux-kernel-call-graphs.html | |
| $ git diff | |
| diff --git a/Makefile b/Makefile | |
| index c43d825a3c4c..3b9f43a112b8 100644 | |
| --- a/Makefile | |
| +++ b/Makefile | |
| @@ -523,7 +523,7 @@ KBUILD_AFLAGS := -D__ASSEMBLY__ -fno-PIE |
davidlohr
/ mmap_sem_to_rangelock.ccocci
Created
May 20, 2019 18:20
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| // Copyright (C) Davidlohr Bueso, 2018. | |
| // | |
| // Convert the infamous mmap_sem to a range lock. | |
| // Usage within the kernel source: | |
| // | |
| // $ make coccicheck MODE=patch COCCI=/path/to/mmap_sem.cocci | |
| virtual patch | |
| virtual context | |
| virtual org |
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