[LTP] [PATCH] madvise06: wait a bit after madvise() call
Jan Stancek
jstancek@redhat.com
Wed Jul 20 16:37:42 CEST 2016
On 07/19/2016 10:57 AM, Li Wang wrote:
>>
>> My impression was that kernel bug was consistently reproducible,
>> if not then let's replace the loop with one bigger sleep.
>
> Sorry, I remember it's not, from what I test on an bad (unfix) kernel.
> it always report PASS with this patch.
Attached is a different approach, that watches progress of SwapCached
from /proc/meminfo and as soon as it sees 128M increase it takes that
as PASS or gives up after 5 seconds with FAIL.
GOOD kernel:
tst_test.c:701: INFO: Timeout per run is 300s
madvise06.c:98: INFO: SwapCached (before madvise): 53576
madvise06.c:113: INFO: SwapCached (after madvise): 568080
madvise06.c:115: PASS: Regression test pass
BAD kernel:
# ./madvise06
tst_test.c:701: INFO: Timeout per run is 300s
madvise06.c:98: INFO: SwapCached (before madvise): 43712
madvise06.c:113: INFO: SwapCached (after madvise): 45636
madvise06.c:117: FAIL: Bug has been reproduced
If you still have the setup, can you try how reliable is this approach?
Regards,
Jan
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/*
* Copyright (c) 2016 Red Hat, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/*
* DESCRIPTION
*
* Page fault occurs in spite that madvise(WILLNEED) system call is called
* to prefetch the page. This issue is reproduced by running a program
* which sequentially accesses to a shared memory and calls madvise(WILLNEED)
* to the next page on a page fault.
*
* This bug is present in all RHEL7 versions. It looks like this was fixed in
* mainline kernel > v3.15 by the following patch:
*
* commit 55231e5c898c5c03c14194001e349f40f59bd300
* Author: Johannes Weiner <hannes@cmpxchg.org>
* Date: Thu May 22 11:54:17 2014 -0700
*
* mm: madvise: fix MADV_WILLNEED on shmem swapouts
*/
#include <errno.h>
#include <stdio.h>
#include <sys/sysinfo.h>
#include "tst_test.h"
#define CHUNK_SZ (512*1024*1024L)
#define MAX_ALLOC_CHUNKS 200L
#define PASS_THRESHOLD_KB (CHUNK_SZ / 1024 / 4)
static int pg_sz;
struct sysinfo sys_buf_start;
static void setup(void)
{
sysinfo(&sys_buf_start);
if (sys_buf_start.totalram > (MAX_ALLOC_CHUNKS - 1) * CHUNK_SZ)
tst_brk(TCONF, "System RAM is too large, skip test");
if (sys_buf_start.freeswap < 2 * CHUNK_SZ)
tst_brk(TCONF, "System swap is too small");
pg_sz = getpagesize();
}
static void test_advice_willneed(void)
{
int i;
char *src;
char *dst[MAX_ALLOC_CHUNKS];
long swapcached_start, swapcached;
struct sysinfo sys_buf;
/* allocate source memory */
src = SAFE_MMAP(NULL, CHUNK_SZ, PROT_READ | PROT_WRITE,
MAP_SHARED | MAP_ANONYMOUS,
-1, 0);
/* allocate destination memory (array) */
for (i = 0; i < MAX_ALLOC_CHUNKS; ++i)
dst[i] = SAFE_MMAP(NULL, CHUNK_SZ,
PROT_READ | PROT_WRITE,
MAP_SHARED | MAP_ANONYMOUS,
-1, 0);
/* memmove source to each destination memories (for SWAP-OUT) */
i = 0;
while (i < MAX_ALLOC_CHUNKS) {
memmove(dst[i], src, CHUNK_SZ);
i++;
sysinfo(&sys_buf);
if (sys_buf.freeswap + CHUNK_SZ < sys_buf_start.freeswap)
break;
}
SAFE_MUNMAP(src, CHUNK_SZ);
sync();
SAFE_FILE_LINES_SCANF("/proc/meminfo", "SwapCached: %ld",
&swapcached_start);
tst_res(TINFO, "SwapCached (before madvise): %ld", swapcached_start);
/* Do madvise() to dst[0] */
TEST(madvise(dst[0], CHUNK_SZ, MADV_WILLNEED));
if (TEST_RETURN == -1)
tst_brk(TBROK | TERRNO, "madvise failed");
i = 0;
do {
i++;
usleep(100000);
SAFE_FILE_LINES_SCANF("/proc/meminfo", "SwapCached: %ld",
&swapcached);
} while (i < 50 && swapcached < swapcached_start + PASS_THRESHOLD_KB);
tst_res(TINFO, "SwapCached (after madvise): %ld", swapcached);
if (swapcached > swapcached_start + PASS_THRESHOLD_KB)
tst_res(TPASS, "Regression test pass");
else
tst_res(TFAIL, "Bug has been reproduced");
for (i = 0; i < MAX_ALLOC_CHUNKS; ++i)
SAFE_MUNMAP(dst[i], CHUNK_SZ);
}
static struct tst_test test = {
.tid = "madvise06",
.test_all = test_advice_willneed,
.setup = setup,
};
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