ghc runtime by default (otherwise depending on a "configure" option) does memory allocation on their own by first mmapping a 1 TB range of memory into the process and then parceling out chunks from it. If one of the chunks is not needed, the kernel needs to be informed - otherwise the system would quickly run out of available RAM. ghc does that via madvise(2). There are two options when doing this informing: MADV_FREE - Means "I don't need this range or the data in it any more". Kernel promises to fail later accesses to it. MADV_DONTNEED - Means "I don't need this range right now - and I don't need the data in it anymore". Kernel promises to make later accesses to it succeed (if necessary by providing a new page initialized with zeroes). MADV_FREE was introduced in Linux 4.5. glibc 2.25 and later always define MADV_FREE. Unpatched ghc 8.0.2 will use either MADV_FREE or MADV_DONTNEED, determined at ghc compile time. Which of them will actually succeed is determined by the Linux kernel at run time. This patch makes ghc try MADV_FREE. If it doesn't work, it falls back to MADV_DONTNEED. The end result is that ghc programs free their memory with Linux < 4.5 again. See https://git.haskell.org/ghc.git/commitdiff/6576bf83cdf4eac05eb88a24aa934a736c91e3da for more information. --- a/rts/posix/OSMem.c +++ b/rts/posix/OSMem.c @@ -541,11 +541,24 @@ void osDecommitMemory(void *at, W_ size) #ifdef MADV_FREE // Try MADV_FREE first, FreeBSD has both and MADV_DONTNEED - // just swaps memory out + // just swaps memory out. Linux >= 4.5 has both DONTNEED and FREE; either + // will work as they both allow the system to free anonymous pages. + // It is important that we try both methods as the kernel which we were + // built on may differ from the kernel we are now running on. r = madvise(at, size, MADV_FREE); -#else - r = madvise(at, size, MADV_DONTNEED); + if(r < 0) { + if (errno == EINVAL) { + // Perhaps the system doesn't support MADV_FREE; fall-through and + // try MADV_DONTNEED. + } else { + sysErrorBelch("unable to decommit memory"); + } + } else { + return; + } #endif + + r = madvise(at, size, MADV_DONTNEED); if(r < 0) sysErrorBelch("unable to decommit memory"); } th> 2019-03-24Add (gnu system keyboard)....* gnu/system/keyboard.scm: New file. * gnu/local.mk (GNU_SYSTEM_MODULES): Add it. * gnu.scm (%public-modules): Add it. Ludovic Courtès 2017-11-08gnu: Improve error reporting of the use-.*modules macros....Suggested by Julien Lepiller and myglc2 at <https://lists.gnu.org/archive/html/guix-devel/2017-11/msg00106.html>. * gnu.scm (%try-use-modules): New procedure. (package-module-hint, service-module-hint): New procedures. (try-use-modules): New macro. (use-package-modules, use-service-modules, use-system-modules): Use it. * tests/guix-system.sh: Test it. Ludovic Courtès 2017-05-16bootloader: Add extlinux support....* gnu/bootloader.scm: New file. * gnu/bootloader/extlinux.scm: New file. * gnu/bootloader/grub.scm: New file. * gnu/local.mk: Build new files. * gnu/system.scm: Adapt to new bootloader api. * gnu/scripts/system.scm: Adapt to new bootloader api. * gnu.scm: Remove (gnu system grub) and replace by (gnu bootloader) and (gnu bootloader grub) modules. * gnu/system/grub.scm: Moved content to gnu/bootloader/grub.scm. * gnu/system/vm: Replace (gnu system grub) module by (gnu bootloader). * gnu/tests.scm: Ditto. * gnu/tests/nfs.scm: Ditto. Mathieu Othacehe