Note: This patch is also now in a git tree at:
git://oss.oracle.com/git/djm/tmem.git#selfballoon-fix-v2
The balloon driver's "current_pages" is very different from
totalram_pages. Self-ballooning needs to be driven by
the latter. Also, Committed_AS doesn't account for pages
used by the kernel so enforce a floor for when there are little
or no user-space threads using memory. The floor function
includes a "safety margin" tuneable in case we discover later
that the floor function is still too aggressive in some workloads,
though likely it will not be needed.
Changes since version 1:
- tuneable safety margin added
[v2: konrad.wilk@xxxxxxxxxx: make safety margin tuneable]
Signed-off-by: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>
diff --git a/drivers/xen/xen-selfballoon.c b/drivers/xen/xen-selfballoon.c
index 6ea852e..ceaada6 100644
--- a/drivers/xen/xen-selfballoon.c
+++ b/drivers/xen/xen-selfballoon.c
@@ -93,6 +93,12 @@ static unsigned int selfballoon_uphysteresis __read_mostly =
1;
/* In HZ, controls frequency of worker invocation. */
static unsigned int selfballoon_interval __read_mostly = 5;
+/*
+ * Scale factor for safety margin for minimum selfballooning target for
balloon.
+ * Default adds about 3% (4/128) of max_pfn.
+ */
+static unsigned int selfballoon_safety_margin = 4;
+
static void selfballoon_process(struct work_struct *work);
static DECLARE_DELAYED_WORK(selfballoon_worker, selfballoon_process);
@@ -195,14 +201,13 @@ __setup("selfballooning", xen_selfballooning_setup);
*/
static void selfballoon_process(struct work_struct *work)
{
- unsigned long cur_pages, goal_pages, tgt_pages;
+ unsigned long cur_pages, goal_pages, tgt_pages, floor_pages;
bool reset_timer = false;
if (xen_selfballooning_enabled) {
- cur_pages = balloon_stats.current_pages;
+ cur_pages = totalram_pages;
tgt_pages = cur_pages; /* default is no change */
- goal_pages = percpu_counter_read_positive(&vm_committed_as) +
- balloon_stats.current_pages - totalram_pages;
+ goal_pages = percpu_counter_read_positive(&vm_committed_as);
#ifdef CONFIG_FRONTSWAP
/* allow space for frontswap pages to be repatriated */
if (frontswap_selfshrinking && frontswap_enabled)
@@ -217,7 +222,13 @@ static void selfballoon_process(struct work_struct *work)
((goal_pages - cur_pages) /
selfballoon_uphysteresis);
/* else if cur_pages == goal_pages, no change */
- balloon_set_new_target(tgt_pages);
+ floor_pages = totalreserve_pages +
+ ((roundup_pow_of_two(max_pfn) / 128) *
+ selfballoon_safety_margin);
+ if (tgt_pages < floor_pages)
+ tgt_pages = floor_pages;
+ balloon_set_new_target(tgt_pages +
+ balloon_stats.current_pages - totalram_pages);
reset_timer = true;
}
#ifdef CONFIG_FRONTSWAP
@@ -340,6 +351,30 @@ static ssize_t store_selfballoon_uphys(struct sys_device
*dev,
static SYSDEV_ATTR(selfballoon_uphysteresis, S_IRUGO | S_IWUSR,
show_selfballoon_uphys, store_selfballoon_uphys);
+SELFBALLOON_SHOW(selfballoon_safety_margin, "%d\n", selfballoon_safety_margin);
+
+static ssize_t store_selfballoon_safety_margin(struct sys_device *dev,
+ struct sysdev_attribute *attr,
+ const char *buf,
+ size_t count)
+{
+ unsigned long val;
+ int err;
+
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+ err = strict_strtoul(buf, 10, &val);
+ if (err || val == 0 || val > 128)
+ return -EINVAL;
+ selfballoon_safety_margin = val;
+ return count;
+}
+
+static SYSDEV_ATTR(selfballoon_safety_margin, S_IRUGO | S_IWUSR,
+ show_selfballoon_safety_margin,
+ store_selfballoon_safety_margin);
+
+
#ifdef CONFIG_FRONTSWAP
SELFBALLOON_SHOW(frontswap_selfshrinking, "%d\n", frontswap_selfshrinking);
@@ -421,6 +456,7 @@ static struct attribute *selfballoon_attrs[] = {
&attr_selfballoon_interval.attr,
&attr_selfballoon_downhysteresis.attr,
&attr_selfballoon_uphysteresis.attr,
+ &attr_selfballoon_safety_margin.attr,
#ifdef CONFIG_FRONTSWAP
&attr_frontswap_selfshrinking.attr,
&attr_frontswap_hysteresis.attr,
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