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From 6576bf83cdf4eac05eb88a24aa934a736c91e3da Mon Sep 17 00:00:00 2001
From: Ben Gamari <bgamari.foss@gmail.com>
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
|
