From 6576bf83cdf4eac05eb88a24aa934a736c91e3da Mon Sep 17 00:00:00 2001 From: Ben Gamari Date: Thu, 1 Dec 2016 12:55:23 -0500 Subject: [PATCH] rts: Ensure we always give MADV_DONTNEED a chance in osDecommitMemory As described in #12865, newer Linux kernels support both MADV_FREE and MADV_DONTNEED. Previously a runtime would fail to try MADV_DONTNEED if MADV_FREE failed (e.g. since the kernel which the image is running on doesn't support the latter). Now we try MADV_DONTNEED if MADV_FREE failed to ensure that binaries compiled on a kernel supporting MADV_FREE don't fail on decommit. Test Plan: Validate Reviewers: austin, erikd, simonmar Reviewed By: simonmar Subscribers: thomie Differential Revision: https://phabricator.haskell.org/D2780 GHC Trac Issues: #12865 --- rts/posix/OSMem.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) diff --git a/rts/posix/OSMem.c b/rts/posix/OSMem.c index 5291745..beffeda 100644 --- 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"); } -- 1.9.1