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Link-Time Optimization To Speed Up The Linux Kernel

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  • alexcortes
    replied
    Debian & Gentoo

    Hi,

    Debian already have plans to switch to LLVM and Gentoo is talking about. The big isssue seems the GNU useland.

    Gentoo Forum
    Gentoo BugTracker
    Debian Package Rebuild

    Leave a comment:


  • ninez
    replied
    Originally posted by uid313 View Post
    I'd like to see someone try compile Linux with;
    * GCC
    * Microsoft Compiler
    * LLVM / Clang / DragonEgg
    * PCC, TCC
    * Intel C Compiler
    * Open64
    Out of those, i personally have used GCC (obviously), ICC (intel C compiler) and Clang/LLVM (using the lll-project listed above) to successfully compile the linux kernel.

    I think i may have also tried Open64 5.0 but it failed. The rest i have not tried but would assume they would all fail OOTB.

    Leave a comment:


  • uid313
    replied
    Originally posted by mark45 View Post
    Afaik LLVM is mostly driven by Apple and Apple has no interest in making LLVM build the Linux kernel.
    But there have been attempts to make Linux compile under LLVM (or was it Intel C Compiler?).
    Someone managed to compile parts of it, not all, and maybe with some patches.

    Some people in the Linux community are interested in seeing Linux compile under LLVM, because it is argued that having Linux compile under many compilers will improve code quality.

    Originally posted by mark45 View Post
    Since Linux uses GCC specific behavior I'd expect LLVM to take several years (if ever) until it's good enough to be used by default mainstream.
    Isn't GCC-specific behavior bad?
    Shouldn't it be ANSI/ISO-compatible?

    Originally posted by mark45 View Post
    The need for a new compiler for Linux is exaggerated and over-appreciated (like Facebook hehe), GCC is good enough and improving (being cleaned up, moving to C++, LTO).
    Yeah, I know. GCC is much faster than LLVM.
    But would be nice if Linux compiled cleanly with several compilers.

    I'd like to see someone try compile Linux with;
    * GCC
    * Microsoft Compiler
    * LLVM / Clang / DragonEgg
    * PCC, TCC
    * Intel C Compiler
    * Open64

    Leave a comment:


  • ninez
    replied
    Originally posted by uid313 View Post
    On related note, how much progress has been on LLVM to compile Linux?
    I remember hearing attempts to make LLVM compile Linux before.

    I know GCC is much faster than LLVM.
    But what is the status of Linux on LLVM?


    People have been messing around with the LLVM + linux kernel combo for a long time via the work done at the University of Illinois...

    There also happens to be this project, that consolidates that work (the lll work) and others;



    Originally posted by mark45 View Post
    Afaik LLVM is mostly driven by Apple and Apple has no interest in making LLVM build the Linux kernel.
    it doesn't require Apple's blessing, nor them to do the work in order for LLVM to build the kernel. They also don't happen to be the only company/party using LLVM, nor the only company/party contributing to CLang/LLVM. What it actually requires is people hacking on code (both Linux kernel and Clang/LLVM code), fixing issues and then submitting their patches upstream to both projects,
    Last edited by ninez; 19 August 2012, 01:23 PM.

    Leave a comment:


  • GreatEmerald
    replied
    Well, that's interesting. Once this gets implemented, it will be awesome news for slow devices on Gentoo using distcc. Also, you could compile a kernel normally, see if it works out right, and then in spare time compile it with the optimizations. I just wonder how much difference they'll make.

    Leave a comment:


  • mark45
    replied
    Originally posted by uid313 View Post
    On related note, how much progress has been on LLVM to compile Linux?
    I remember hearing attempts to make LLVM compile Linux before.

    I know GCC is much faster than LLVM.
    But what is the status of Linux on LLVM?
    Afaik LLVM is mostly driven by Apple and Apple has no interest in making LLVM build the Linux kernel.

    Since Linux uses GCC specific behavior I'd expect LLVM to take several years (if ever) until it's good enough to be used by default mainstream.

    The need for a new compiler for Linux is exaggerated and over-appreciated (like Facebook hehe), GCC is good enough and improving (being cleaned up, moving to C++, LTO).

    Leave a comment:


  • curaga
    replied
    Very nice, I'd like to see this in.

    OTOH, I recall Denys Vlasenko's similar patchset earlier to enable the kernel to build with -ffunction-sections -fdata-sections (resulting in 10-15% smaller binary) was not merged.

    Leave a comment:


  • uid313
    replied
    LLVM

    On related note, how much progress has been on LLVM to compile Linux?
    I remember hearing attempts to make LLVM compile Linux before.

    I know GCC is much faster than LLVM.
    But what is the status of Linux on LLVM?

    Leave a comment:


  • phoronix
    started a topic Link-Time Optimization To Speed Up The Linux Kernel

    Link-Time Optimization To Speed Up The Linux Kernel

    Phoronix: Link-Time Optimization To Speed Up The Linux Kernel

    An extensive set of patches have been published that allow the Linux kernel to be built with GCC's LTO (Link-Time Optimization) support for generating a faster Linux kernel binary but at the cost of much greater compile times...

    Phoronix, Linux Hardware Reviews, Linux hardware benchmarks, Linux server benchmarks, Linux benchmarking, Desktop Linux, Linux performance, Open Source graphics, Linux How To, Ubuntu benchmarks, Ubuntu hardware, Phoronix Test Suite
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