* Matthias Clasen: > On Wed, Jul 6, 2022 at 3:06 PM Florian Weimer <fweimer@xxxxxxxxxx> wrote: > >> If the GNOME's sysprof does not work with Fedora, fix it or use >> something else. Do not change how Fedora is built. > > The result of that attitude is that performance work in the desktop > space is happening on GNOME OS images, or in Flatpak runtimes instead > of on Fedora. Which is a bit sad for Fedora as a supposedly > developer-friendly environment. My comment was specifically about sysprof. I've been told that the GNOME developers will not even consider anything else. This means that we need to fix sysprof. If we do that, it will be possible to use GNOME OS for profiling on older CPUs, and hardware-assisted backtraces on newer CPUs on Fedora (at least Skylake and Zen 3, especially once we've got userspace SHSTK support). Even if this proposal is not accepted, I think we can collaborate on a couple of things: * Enhance sysprof with LBR and SHSTK support. * Enable userspace backtrace generation from BPF without frame pointers (possibly by using LBR and SHSTK at first). * Investigate use of the Systemtap and elfutils unwinders in these tools. * Speed up decoding of DWARF data structures using the BMI instruction sets (which only operate on scalar registers and should therefore be usable even within the kernel). According to <https://lore.kernel.org/all/c54327dc-75c9-db48-f7c1-59f9fcfca26f@xxxxxxx/> that's a major source of DWARF processing overhead, and I don't think it has to be. I'll try to get confirmation that it is technically feasible in priciple to use SHSTK to get arbitrarily deep backtraces from kernel space for userspace applications. If we can get SHSTK to work, the value of the DWARF integration and performance work will diminish fairly quickly because most developers will soon have CPUs with fairly deep (32 entry) LBR buffers, SHSTK support, or both. Thanks, Florian _______________________________________________ devel mailing list -- devel@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to devel-leave@xxxxxxxxxxxxxxxxxxxxxxx Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/devel@xxxxxxxxxxxxxxxxxxxxxxx Do not reply to spam on the list, report it: https://pagure.io/fedora-infrastructure
