To maximise efficiency of anti-fragmentation, pageblocks must be kept free
from mixing page types. The minimum value for this is one pageblock per
zone in the system although even this might be too minimal on x86-32 where
the size of zones vary wildly.
The easiest way to keep pageblocks free from mixing is to increase the value
of min_free_kbytes. This patch compares the current value of min_free_kbytes
with a recommended value and warns if the current value is too low.
Signed-off-by: Mel Gorman <m...@csn.ul.ie>
---
hugeadm.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 46 insertions(+), 0 deletions(-)
diff --git a/hugeadm.c b/hugeadm.c
index 7732659..6db0bfc 100644
--- a/hugeadm.c
+++ b/hugeadm.c
@@ -66,6 +66,8 @@ extern char *optarg;
#define PROCMOUNTS "/proc/mounts"
#define PROCHUGEPAGES_MOVABLE "/proc/sys/vm/hugepages_treat_as_movable"
+#define PROCMINFREEKBYTES "/proc/sys/vm/min_free_kbytes"
+#define PROCZONEINFO "/proc/zoneinfo"
#define FS_NAME "hugetlbfs"
#define MIN_COL 20
#define MAX_SIZE_MNTENT (64 + PATH_MAX + 32 + 128 + 2 * sizeof(int))
@@ -607,6 +609,49 @@ void check_swap()
}
}
+#define ZONEINFO_LINEBUF 1024
+long recommended_minfreekbytes(void)
+{
+ FILE *f;
+ char buf[ZONEINFO_LINEBUF];
+ int nr_zones = 0;
+ long recommended_min;
+ long pageblock_kbytes = kernel_default_hugepage_size() / 1024;
+
+ /* Detect the number of zones in the system */
+ f = fopen(PROCZONEINFO, "r");
+ if (f == NULL) {
+ WARNING("Unable to open " PROCZONEINFO);
+ return 0;
+ }
+ while (fgets(buf, ZONEINFO_LINEBUF, f) != NULL) {
+ if (strncmp(buf, "Node ", 5) == 0)
+ nr_zones++;
+ }
+ fclose(f);
+
+ recommended_min = pageblock_kbytes * nr_zones;
+ return recommended_min;
+}
+
+/*
+ * check_minfreekbytes does not alter the value of min_free_kbytes. It just
+ * reports what the current value is and what it should be
+ */
+void check_minfreekbytes(void)
+{
+ long min_free_kbytes = file_read_ulong(PROCMINFREEKBYTES, NULL);
+ long recommended_min = recommended_minfreekbytes();
+
+ /* There should be at least one pageblock free per zone in the system */
+ if (recommended_min > min_free_kbytes) {
+ printf("\n");
+ printf("The " PROCMINFREEKBYTES " of %ld is too small. To
maximiuse efficiency\n", min_free_kbytes);
+ printf("of fragmentation avoidance, there should be at least
one huge page free per zone\n");
+ printf("in the system which minimally requires a
min_free_kbytes value of %ld\n", recommended_min);
+ }
+}
+
void add_temp_swap(long page_size)
{
char path[PATH_MAX];
@@ -941,6 +986,7 @@ void explain()
pool_list();
printf("\nHuge page sizes with configured pools:\n");
page_sizes(0);
+ check_minfreekbytes();
check_swap();
printf("\nNote: Permanent swap space should be preferred when dynamic "
"huge page pools are used.\n");
--
1.6.3.3
------------------------------------------------------------------------------
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