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authorDanny Milosavljevic <dannym@scratchpost.org>2018-02-15 17:19:28 +0100
committerLeo Famulari <leo@famulari.name>2018-02-16 12:41:01 -0500
commitf6cccefed599e06a814b702aa79b8a09f01ec41c (patch)
treeb66a3487ad79bb59b716ff10088490d15fc8c843 /gnu/packages/patches
parent4aa0a1df2dd89ba0e5f76d33b37383fdb530e0b8 (diff)
downloadguix-f6cccefed599e06a814b702aa79b8a09f01ec41c.tar
guix-f6cccefed599e06a814b702aa79b8a09f01ec41c.tar.gz
gnu: ghc: Make memory allocator decommit memory on Linux < 4.5.
* gnu/packages/patches/ghc-8.0-fall-back-to-madv_dontneed.patch: New file. * gnu/local.mk (dist_patch_DATA): Add it. * gnu/packages/haskell.scm (ghc-8): Use it.
Diffstat (limited to 'gnu/packages/patches')
-rw-r--r--gnu/packages/patches/ghc-8.0-fall-back-to-madv_dontneed.patch61
1 files changed, 61 insertions, 0 deletions
diff --git a/gnu/packages/patches/ghc-8.0-fall-back-to-madv_dontneed.patch b/gnu/packages/patches/ghc-8.0-fall-back-to-madv_dontneed.patch
new file mode 100644
index 0000000000..1838c5bd35
--- /dev/null
+++ b/gnu/packages/patches/ghc-8.0-fall-back-to-madv_dontneed.patch
@@ -0,0 +1,61 @@
+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");
+ }