Add support for reads/writes from buffers backed by hugepages.
This can be enabled through the '-h' flag. This flag should only be used
on systems where THP capabilities are enabled.
This is motivated by a recent bug that was due to faulty handling of
userspace buffers backed by hugepages. This patch is a mitigation
against problems like this in the future.
Signed-off-by: Joanne Koong <joannelkoong@xxxxxxxxx>
Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>
Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx>
---
ltp/fsx.c | 166 +++++++++++++++++++++++++++++++++++++++++++++++++-----
1 file changed, 153 insertions(+), 13 deletions(-)
diff --git a/ltp/fsx.c b/ltp/fsx.c
index 41933354..3be383c6 100644
--- a/ltp/fsx.c
+++ b/ltp/fsx.c
@@ -190,6 +190,16 @@ int o_direct; /* -Z */
int aio = 0;
int uring = 0;
int mark_nr = 0;
+int hugepages = 0; /* -h flag */
+
+/* Stores info needed to periodically collapse hugepages */
+struct hugepages_collapse_info {
+ void *orig_good_buf;
+ long good_buf_size;
+ void *orig_temp_buf;
+ long temp_buf_size;
+};
+struct hugepages_collapse_info hugepages_info;
int page_size;
int page_mask;
@@ -2471,7 +2481,7 @@ void
usage(void)
{
fprintf(stdout, "usage: %s",
- "fsx [-dfknqxyzBEFHIJKLORWXZ0]\n\
+ "fsx [-dfhknqxyzBEFHIJKLORWXZ0]\n\
[-b opnum] [-c Prob] [-g filldata] [-i logdev] [-j logid]\n\
[-l flen] [-m start:end] [-o oplen] [-p progressinterval]\n\
[-r readbdy] [-s style] [-t truncbdy] [-w writebdy]\n\
@@ -2483,8 +2493,11 @@ usage(void)
-d: debug output for all operations\n\
-e: pollute post-eof on size changes (default 0)\n\
-f: flush and invalidate cache after I/O\n\
- -g X: write character X instead of random generated data\n\
- -i logdev: do integrity testing, logdev is the dm log writes device\n\
+ -g X: write character X instead of random generated data\n"
+#ifdef MADV_COLLAPSE
+" -h hugepages: use buffers backed by hugepages for reads/writes\n"
+#endif
+" -i logdev: do integrity testing, logdev is the dm log writes device\n\
-j logid: prefix debug log messsages with this id\n\
-k: do not truncate existing file and use its size as upper bound on file size\n\
-l flen: the upper bound on file size (default 262144)\n\
@@ -2833,11 +2846,41 @@ __test_fallocate(int mode, const char *mode_str)
#endif
}
+/*
+ * Reclaim may break up hugepages, so do a best-effort collapse every once in
+ * a while.
+ */
+static void
+collapse_hugepages(void)
+{
+#ifdef MADV_COLLAPSE
+ int ret;
+
+ /* re-collapse every 16k fsxops after we start */
+ if (!numops || (numops & ((1U << 14) - 1)))
+ return;
+
+ ret = madvise(hugepages_info.orig_good_buf,
+ hugepages_info.good_buf_size, MADV_COLLAPSE);
+ if (ret)
+ prt("collapsing hugepages for good_buf failed (numops=%llu): %s\n",
+ numops, strerror(errno));
+ ret = madvise(hugepages_info.orig_temp_buf,
+ hugepages_info.temp_buf_size, MADV_COLLAPSE);
+ if (ret)
+ prt("collapsing hugepages for temp_buf failed (numops=%llu): %s\n",
+ numops, strerror(errno));
+#endif
+}
+
bool
keep_running(void)
{
int ret;
+ if (hugepages)
+ collapse_hugepages();
+
if (deadline.tv_nsec) {
struct timespec now;
@@ -2856,6 +2899,103 @@ keep_running(void)
return numops-- != 0;
}
+static long
+get_hugepage_size(void)
+{
+ const char str[] = "Hugepagesize:";
+ size_t str_len = sizeof(str) - 1;
+ unsigned int hugepage_size = 0;
+ char buffer[64];
+ FILE *file;
+
+ file = fopen("/proc/meminfo", "r");
+ if (!file) {
+ prterr("get_hugepage_size: fopen /proc/meminfo");
+ return -1;
+ }
+ while (fgets(buffer, sizeof(buffer), file)) {
+ if (strncmp(buffer, str, str_len) == 0) {
+ sscanf(buffer + str_len, "%u", &hugepage_size);
+ break;
+ }
+ }
+ fclose(file);
+ if (!hugepage_size) {
+ prterr("get_hugepage_size: failed to find "
+ "hugepage size in /proc/meminfo\n");
+ return -1;
+ }
+
+ /* convert from KiB to bytes */
+ return hugepage_size << 10;
+}
+
+static void *
+init_hugepages_buf(unsigned len, int hugepage_size, int alignment, long *buf_size)
+{
+ void *buf = NULL;
+#ifdef MADV_COLLAPSE
+ int ret;
+ long size = roundup(len, hugepage_size) + alignment;
+
+ ret = posix_memalign(&buf, hugepage_size, size);
+ if (ret) {
+ prterr("posix_memalign for buf");
+ return NULL;
+ }
+ memset(buf, '\0', size);
+ ret = madvise(buf, size, MADV_COLLAPSE);
+ if (ret) {
+ prterr("madvise collapse for buf");
+ free(buf);
+ return NULL;
+ }
+
+ *buf_size = size;
+#endif
+ return buf;
+}
+
+static void
+init_buffers(void)
+{
+ int i;
+
+ original_buf = (char *) malloc(maxfilelen);
+ for (i = 0; i < maxfilelen; i++)
+ original_buf[i] = random() % 256;
+ if (hugepages) {
+ long hugepage_size = get_hugepage_size();
+ if (hugepage_size == -1) {
+ prterr("get_hugepage_size()");
+ exit(102);
+ }
+ good_buf = init_hugepages_buf(maxfilelen, hugepage_size, writebdy,
+ &hugepages_info.good_buf_size);
+ if (!good_buf) {
+ prterr("init_hugepages_buf failed for good_buf");
+ exit(103);
+ }
+ hugepages_info.orig_good_buf = good_buf;
+
+ temp_buf = init_hugepages_buf(maxoplen, hugepage_size, readbdy,
+ &hugepages_info.temp_buf_size);
+ if (!temp_buf) {
+ prterr("init_hugepages_buf failed for temp_buf");
+ exit(103);
+ }
+ hugepages_info.orig_temp_buf = temp_buf;
+ } else {
+ unsigned long good_buf_len = maxfilelen + writebdy;
+ unsigned long temp_buf_len = maxoplen + readbdy;
+
+ good_buf = calloc(1, good_buf_len);
+ temp_buf = calloc(1, temp_buf_len);
+ }
+ good_buf = round_ptr_up(good_buf, writebdy, 0);
+ temp_buf = round_ptr_up(temp_buf, readbdy, 0);
+}
+
static struct option longopts[] = {
{"replay-ops", required_argument, 0, 256},
{"record-ops", optional_argument, 0, 255},
@@ -2883,7 +3023,7 @@ main(int argc, char **argv)
setvbuf(stdout, (char *)0, _IOLBF, 0); /* line buffered stdout */
while ((ch = getopt_long(argc, argv,
- "0b:c:de:fg:i:j:kl:m:no:p:qr:s:t:uw:xyABD:EFJKHzCILN:OP:RS:UWXZ",
+ "0b:c:de:fg:hi:j:kl:m:no:p:qr:s:t:uw:xyABD:EFJKHzCILN:OP:RS:UWXZ",
longopts, NULL)) != EOF)
switch (ch) {
case 'b':
@@ -2916,6 +3056,14 @@ main(int argc, char **argv)
case 'g':
filldata = *optarg;
break;
+ case 'h':
+#ifndef MADV_COLLAPSE
+ fprintf(stderr, "MADV_COLLAPSE not supported. "
+ "Can't support -h\n");
+ exit(86);
+#endif
+ hugepages = 1;
+ break;
case 'i':
integrity = 1;
logdev = strdup(optarg);
@@ -3229,15 +3377,7 @@ main(int argc, char **argv)
exit(95);
}
}
- original_buf = (char *) malloc(maxfilelen);
- for (i = 0; i < maxfilelen; i++)
- original_buf[i] = random() % 256;
- good_buf = (char *) malloc(maxfilelen + writebdy);
- good_buf = round_ptr_up(good_buf, writebdy, 0);
- memset(good_buf, '\0', maxfilelen);
- temp_buf = (char *) malloc(maxoplen + readbdy);
- temp_buf = round_ptr_up(temp_buf, readbdy, 0);
- memset(temp_buf, '\0', maxoplen);
+ init_buffers();
if (lite) { /* zero entire existing file */
ssize_t written;
--
2.47.1
