Adjust the kernel's idea of the end of the data segment (the 'brk' value)
to match user space when we remap the data segment onto hugepages.
Signed-off-by: Andrew Hastings <[EMAIL PROTECTED]> on behalf of Cray Inc.
---
While I was running some of the libhugetlbfs linker tests under strace,
I noticed brk() was failing. Poking around in /proc/self/maps I
discovered why.
Breaking brk() (no pun intended) is bad because (1) it causes malloc to
make two system calls every time it needs to grow the heap (a failing
sbrk and then an mmap) and (2) the process's address space ends up with
lots of little VMAs.
Tested both 32- and 64-bit binaries under SUSE 10 on x86-64.
-Andrew Hastings
Cray Inc.
diff -ruNp libhugetlbfs-1.2/elflink.c libhugetlbfs-1.2-modified/elflink.c
--- libhugetlbfs-1.2/elflink.c 2007-09-10 08:27:44.000000000 -0500
+++ libhugetlbfs-1.2-modified/elflink.c 2007-09-18 12:17:04.932081000 -0500
@@ -923,6 +923,23 @@ static void remap_segments(struct seg_in
long hpage_size = gethugepagesize();
int i;
void *p;
+ void *oldbrk, *newbrk;
+
+ /*
+ * Adjust the brk value to the end of the data segment.
+ */
+ newbrk = oldbrk = sbrk(0);
+ DEBUG("Current brk=%p\n", oldbrk);
+ for (i = 0; i < num; i++) {
+ unsigned long mapsize = ALIGN(seg[i].memsz, hpage_size);
+
+ DEBUG("%p - %p\n", seg[i].vaddr, seg[i].vaddr + mapsize);
+ if (seg[i].vaddr <= oldbrk && oldbrk < seg[i].vaddr + mapsize)
+ newbrk = seg[i].vaddr + mapsize;
+ }
+ DEBUG("New brk=%p\n", newbrk);
+ if (newbrk != oldbrk)
+ brk(newbrk);
/*
* XXX: The bogus call to mmap below forces ld.so to resolve the
diff -ruNp libhugetlbfs-1.2/tests/Makefile
libhugetlbfs-1.2-modified/tests/Makefile
--- libhugetlbfs-1.2/tests/Makefile 2007-09-10 08:27:44.000000000 -0500
+++ libhugetlbfs-1.2-modified/tests/Makefile 2007-09-18 12:25:43.005889000
-0500
@@ -11,7 +11,7 @@ LIB_TESTS_64 = straddle_4GB huge_at_4GB_
huge_below_4GB_normal_above
NOLIB_TESTS = malloc malloc_manysmall dummy
LDSCRIPT_TESTS = zero_filesize_segment
-HUGELINK_TESTS = linkhuge linkhuge_nofd linkshare
+HUGELINK_TESTS = linkhuge linkhuge_nofd linkshare brk-align
STRESS_TESTS = mmap-gettest mmap-cow shm-gettest shm-getraw shm-fork
HELPERS = get_hugetlbfs_path
BADTOOLCHAIN = bad-toolchain.sh
diff -ruNp libhugetlbfs-1.2/tests/brk-align.c
libhugetlbfs-1.2-modified/tests/brk-align.c
--- libhugetlbfs-1.2/tests/brk-align.c 1969-12-31 18:00:00.000000000 -0600
+++ libhugetlbfs-1.2-modified/tests/brk-align.c 2007-09-18 12:25:42.983191000
-0500
@@ -0,0 +1,36 @@
+/*
+ * This file is subject to the terms and conditions of the GNU Lesser General
+ * Public License. See the file "LGPL-2.1" in the main directory of this
+ * archive for more details.
+ *
+ * Copyright 2007 Cray Inc. All Rights Reserved.
+ */
+
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include "hugetests.h"
+
+/*
+ * This test verifies that libhugetlbfs adjusts the brk value to the
+ * end of the data segment when it remaps the data segment onto hugepages.
+ */
+
+static int data = 1;
+
+int main(int argc, char **argv)
+{
+ int pagesize;
+
+ test_init(argc, argv);
+
+ if (test_addr_huge(&data) != 1)
+ CONFIG("Data segment not on hugepage");
+
+ pagesize = getpagesize();
+ if (sbrk(pagesize) == (void *)-1)
+ FAIL("sbrk(%d) failed", pagesize);
+
+ PASS();
+}
diff -ruNp libhugetlbfs-1.2/tests/run_tests.sh
libhugetlbfs-1.2-modified/tests/run_tests.sh
--- libhugetlbfs-1.2/tests/run_tests.sh 2007-09-10 08:27:44.000000000 -0500
+++ libhugetlbfs-1.2-modified/tests/run_tests.sh 2007-09-18
12:04:56.933928000 -0500
@@ -169,6 +169,7 @@ functional_tests () {
preload_test HUGETLB_MORECORE=yes malloc_manysmall
elflink_test HUGETLB_VERBOSE=0 linkhuge_nofd # Lib error msgs expected
elflink_test linkhuge
+ run_test xBDT.brk-align
# Sharing tests
elfshare_test linkshare
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