From: Daniel Jordan <daniel.m.jordan@oracle.com>
To: Huang Ying <ying.huang@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Michal Hocko <mhocko@kernel.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Shaohua Li <shli@kernel.org>, Hugh Dickins <hughd@google.com>,
Minchan Kim <minchan@kernel.org>, Rik van Riel <riel@redhat.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
Zi Yan <zi.yan@cs.rutgers.edu>,
Daniel Jordan <daniel.m.jordan@oracle.com>
Subject: Re: [PATCH -V6 00/21] swap: Swapout/swapin THP in one piece
Date: Tue, 23 Oct 2018 05:27:38 -0700 [thread overview]
Message-ID: <20181023122738.a5j2vk554tsx4f6i@ca-dmjordan1.us.oracle.com> (raw)
In-Reply-To: <20181010071924.18767-1-ying.huang@intel.com>
On Wed, Oct 10, 2018 at 03:19:03PM +0800, Huang Ying wrote:
> And for all, Any comment is welcome!
>
> This patchset is based on the 2018-10-3 head of mmotm/master.
There seems to be some infrequent memory corruption with THPs that have been
swapped out: page contents differ after swapin.
Reproducer at the bottom. Part of some tests I'm writing, had to separate it a
little hack-ily. Basically it writes the word offset _at_ each word offset in
a memory blob, tries to push it to swap, and verifies the offset is the same
after swapin.
I ran with THP enabled=always. THP swapin_enabled could be always or never, it
happened with both. Every time swapping occurred, a single THP-sized chunk in
the middle of the blob had different offsets. Example:
** > word corruption gap
** corruption detected 14929920 bytes in (got 15179776, expected 14929920) **
** corruption detected 14929928 bytes in (got 15179784, expected 14929928) **
** corruption detected 14929936 bytes in (got 15179792, expected 14929936) **
...pattern continues...
** corruption detected 17027048 bytes in (got 15179752, expected 17027048) **
** corruption detected 17027056 bytes in (got 15179760, expected 17027056) **
** corruption detected 17027064 bytes in (got 15179768, expected 17027064) **
100.0% of memory was swapped out at mincore time
0.00305% of pages were corrupted (first corrupt word 14929920, last corrupt word 17027064)
The problem goes away with THP enabled=never, and I don't see it on 2018-10-3
mmotm/master with THP enabled=always.
The server had an NVMe swap device and ~760G memory over two nodes, and the
program was always run like this: swap-verify -s $((64 * 2**30))
The kernels had one extra patch, Alexander Duyck's
"dma-direct: Fix return value of dma_direct_supported", which was required to
get them to build.
---------------------------------------8<---------------------------------------
/*
* swap-verify.c - helper to verify contents of swapped out pages
*
* Daniel Jordan <daniel.m.jordan@oracle.com>
*/
#define _GNU_SOURCE
#include <getopt.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <unistd.h>
#define TEST_SUCCESS 0
#define TEST_FAIL 1
#define TEST_SKIP 2
static void usagedie(int exitcode)
{
fprintf(stderr, "usage: swap-verify\n"
" -h show this message\n"
" -s bytes\n");
exit(exitcode);
}
int main(int argc, char **argv)
{
int c, pgsize;
char *pages;
unsigned char *mincore_vec;
size_t i, j, nr_pages_swapped, nr_pages_corrupted;
size_t bytes = 1ul << 30; /* default 1G */
ssize_t bytes_read;
size_t first_corrupt_word, last_corrupt_word, prev_corrupt_word;
while ((c = getopt(argc, argv, "hs:")) != -1) {
switch (c) {
case 'h':
usagedie(0);
break;
case 's':
bytes = strtoul(optarg, NULL, 10);
break;
default:
fprintf(stderr, "unrecognized option %c\n", c);
exit(TEST_SKIP);
}
}
pgsize = getpagesize();
if ((mincore_vec = calloc(bytes / pgsize, 1)) == NULL) {
perror("calloc");
exit(TEST_SKIP);
}
if ((pages = mmap(NULL, bytes, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0)) == MAP_FAILED) {
perror("mmap");
exit(TEST_SKIP);
}
/* Fill pages with a "random" pattern. */
for (i = 0; i < bytes; i += sizeof(unsigned long))
*(unsigned long *)(pages + i) = i;
/* Now fill memory, trying to push the pages just allocated to swap. */
system("./use-mem-total");
/* Is the memory swapped out? */
if (mincore(pages, bytes, mincore_vec) == -1) {
perror("mincore");
exit(TEST_SKIP);
}
nr_pages_swapped = 0;
nr_pages_corrupted = 0;
first_corrupt_word = bytes;
last_corrupt_word = 0;
prev_corrupt_word = bytes;
for (i = 0; i < bytes; i += pgsize) {
bool page_corrupt = false;
if (mincore_vec[i / pgsize] & 1) {
/* Resident, don't bother checking. */
continue;
}
++nr_pages_swapped;
for (j = i; j < i + pgsize; j += sizeof(unsigned long)) {
unsigned long val = *(unsigned long *)(pages + j);
if (val != j) {
if (!page_corrupt)
++nr_pages_corrupted;
page_corrupt = true;
if (j - prev_corrupt_word != sizeof(unsigned long))
fprintf(stderr, "** > word corruption gap\n");
if (j % (1ul << 21) == 0)
fprintf(stderr, "-- THP boundary\n");
if (j < first_corrupt_word)
first_corrupt_word = j;
if (j > last_corrupt_word)
last_corrupt_word = j;
fprintf(stderr, "** corruption detected %lu "
"bytes in (got %lu, expected %lu) **\n",
j, val, j);
prev_corrupt_word = j;
}
}
}
fprintf(stderr, "%.1f%% of memory was swapped out at mincore time\n",
((double)nr_pages_swapped / (bytes / pgsize)) * 100);
if (nr_pages_corrupted) {
fprintf(stderr, "%.5f%% of pages were corrupted (first corrupt "
"word %lu, last corrupt word %lu)\n",
((double)nr_pages_corrupted / (bytes / pgsize)) * 100,
first_corrupt_word, last_corrupt_word);
} else {
fprintf(stderr, "no memory corruption detected\n");
}
return (nr_pages_corrupted) ? TEST_FAIL : TEST_SUCCESS;
}
---------------------------------------8<---------------------------------------
#!/usr/bin/env bash
#
# use-mem-total
#
# Helper that allocates MemTotal and exits immediately. Useful for causing
# swapping of previously allocated memory.
# XXX fix paths
source /path/to/vm-scalability/hw_vars
/path/to/usemem --thread $nr_task --step $pagesize -q --repeat 4 \
$(( mem * 11 / 10 / nr_task )) > /dev/null
---------------------------------------8<---------------------------------------
next prev parent reply other threads:[~2018-10-23 12:27 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-10 7:19 [PATCH -V6 00/21] swap: Swapout/swapin THP in one piece Huang Ying
2018-10-10 7:19 ` [PATCH -V6 01/21] swap: Enable PMD swap operations for CONFIG_THP_SWAP Huang Ying
2018-10-10 7:19 ` [PATCH -V6 02/21] swap: Add __swap_duplicate_locked() Huang Ying
2018-10-10 7:19 ` [PATCH -V6 03/21] swap: Support PMD swap mapping in swap_duplicate() Huang Ying
2018-10-10 7:19 ` [PATCH -V6 04/21] swap: Support PMD swap mapping in put_swap_page() Huang Ying
2018-10-10 7:19 ` [PATCH -V6 05/21] swap: Support PMD swap mapping in free_swap_and_cache()/swap_free() Huang Ying
2018-10-10 7:19 ` [PATCH -V6 06/21] swap: Support PMD swap mapping when splitting huge PMD Huang Ying
2018-10-24 17:25 ` Daniel Jordan
2018-10-25 0:54 ` Huang, Ying
2018-10-25 15:00 ` Daniel Jordan
2018-10-10 7:19 ` [PATCH -V6 07/21] swap: Support PMD swap mapping in split_swap_cluster() Huang Ying
2018-10-10 7:19 ` [PATCH -V6 08/21] swap: Support to read a huge swap cluster for swapin a THP Huang Ying
2018-10-10 7:19 ` [PATCH -V6 09/21] swap: Swapin a THP in one piece Huang Ying
2018-10-10 7:19 ` [PATCH -V6 10/21] swap: Support to count THP swapin and its fallback Huang Ying
2018-10-10 7:19 ` [PATCH -V6 11/21] swap: Add sysfs interface to configure THP swapin Huang Ying
2018-10-10 7:19 ` [PATCH -V6 12/21] swap: Support PMD swap mapping in swapoff Huang Ying
2018-10-10 7:19 ` [PATCH -V6 13/21] swap: Support PMD swap mapping in madvise_free() Huang Ying
2018-10-10 7:19 ` [PATCH -V6 14/21] swap: Support to move swap account for PMD swap mapping Huang Ying
2018-10-24 17:27 ` Daniel Jordan
2018-10-25 1:06 ` Huang, Ying
2018-10-10 7:19 ` [PATCH -V6 15/21] swap: Support to copy PMD swap mapping when fork() Huang Ying
2018-10-10 7:19 ` [PATCH -V6 16/21] swap: Free PMD swap mapping when zap_huge_pmd() Huang Ying
2018-10-10 7:19 ` [PATCH -V6 17/21] swap: Support PMD swap mapping for MADV_WILLNEED Huang Ying
2018-10-10 7:19 ` [PATCH -V6 18/21] swap: Support PMD swap mapping in mincore() Huang Ying
2018-10-10 7:19 ` [PATCH -V6 19/21] swap: Support PMD swap mapping in common path Huang Ying
2018-10-10 7:19 ` [PATCH -V6 20/21] swap: create PMD swap mapping when unmap the THP Huang Ying
2018-10-10 7:19 ` [PATCH -V6 21/21] swap: Update help of CONFIG_THP_SWAP Huang Ying
2018-10-23 12:27 ` Daniel Jordan [this message]
2018-10-24 3:31 ` [PATCH -V6 00/21] swap: Swapout/swapin THP in one piece Huang, Ying
2018-10-24 17:24 ` Daniel Jordan
2018-10-25 0:42 ` Huang, Ying
2018-11-09 1:12 ` Daniel Jordan
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