The state of the art of sysv/posix ipc benchmarking is a combination of ad-hoc programs scattered over the internet. While some mechanisms, such as sysv semaphores, have a lot of coverage, others really lack (message queues), and some are simply non-existent; albeit some of the legacy flavors we aren't too concerned with, other than them being functionally correct.

Consolidate all this by taking the good benchmarks and implement new ones where needed, such as message queues, everything around the 'perf bench' framework. This will both improve the lives of us who hack on kenrel ipc as well as improve coverage overall. Eventually mmtests should be updated as well.

Looking for hackers with the skills:

ipc linux kernel

This project is part of:

Hack Week 18

Activity

  • about 6 years ago: dsterba liked this project.
  • about 6 years ago: dfaggioli liked this project.
  • about 6 years ago: dbueso started this project.
  • about 6 years ago: dbueso added keyword "ipc" to this project.
  • about 6 years ago: dbueso added keyword "linux" to this project.
  • about 6 years ago: dbueso added keyword "kernel" to this project.
  • about 6 years ago: dbueso removed keyword ipclinuxkernel from this project.
  • about 6 years ago: dbueso added keyword "ipclinuxkernel" to this project.
  • about 6 years ago: dbueso originated this project.

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    early stage kdump support by mbrugger

    Project Description

    When we experience a early boot crash, we are not able to analyze the kernel dump, as user-space wasn't able to load the crash system. The idea is to make the crash system compiled into the host kernel (think of initramfs) so that we can create a kernel dump really early in the boot process.

    Goal for the Hackweeks

    1. Investigate if this is possible and the implications it would have (done in HW21)
    2. Hack up a PoC (done in HW22 and HW23)
    3. Prepare RFC series (giving it's only one week, we are entering wishful thinking territory here).

    update HW23

    • I was able to include the crash kernel into the kernel Image.
    • I'll need to find a way to load that from init/main.c:start_kernel() probably after kcsan_init()
    • I workaround for a smoke test was to hack kexec_file_load() systemcall which has two problems:
      1. My initramfs in the porduction kernel does not have a new enough kexec version, that's not a blocker but where the week ended
      2. As the crash kernel is part of init.data it will be already stale once I can call kexec_file_load() from user-space.

    The solution is probably to rewrite the POC so that the invocation can be done from init.text (that's my theory) but I'm not sure if I can reuse the kexec infrastructure in the kernel from there, which I rely on heavily.

    update HW24

    • Day1
      • rebased on v6.12 with no problems others then me breaking the config
      • setting up a new compilation and qemu/virtme env
      • getting desperate as nothing works that used to work
    • Day 2
      • getting to call the invocation of loading the early kernel from __init after kcsan_init()
    • Day 3

      • fix problem of memdup not being able to alloc so much memory... use 64K page sizes for now
      • code refactoring
      • I'm now able to load the crash kernel
      • When using virtme I can boot into the crash kernel, also it doesn't boot completely (major milestone!), crash in elfcorehdr_read_notes()
    • Day 4

      • crash systems crashes (no pun intended) in copy_old_mempage() link; will need to understand elfcorehdr...
      • call path vmcore_init() -> parse_crash_elf_headers() -> elfcorehdr_read() -> read_from_oldmem() -> copy_oldmem_page() -> copy_to_iter()
    • Day 5

      • hacking arch/arm64/kernel/crash_dump.c:copy_old_mempage() to see if crash system really starts. It does.
      • fun fact: retested with more reserved memory and with UEFI FW, host kernel crashes in init but directly starts the crash kernel, so it works (somehow) \o/
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      • fix elfcorehdr so that we actually can make use of all this...
      • test where in the boot __init() chain we can/should call kexec_early_dump()