[PATCH -mm -v2 5/6] mm, swap: Add sysfs interface for VMA based swap readahead

Huang, Ying
2017-06-30T01:45:56Z

The sysfs interface to control the VMA based swap readahead is added
as follow,

/sys/kernel/mm/swap/vma_ra_enabled

Enable the VMA based swap readahead algorithm, or use the original
global swap readahead algorithm.

/sys/kernel/mm/swap/vma_ra_max_order

Set the max order of the readahead window size for the VMA based swap
readahead algorithm.

Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Tim Chen <tim.c.chen@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
---
mm/swap_state.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 47 insertions(+)

diff --git a/mm/swap_state.c b/mm/swap_state.c
index c88eda175ba7..bd483aff543a 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -812,6 +812,51 @@ static ssize_t swap_readahead_total_show(
static struct kobj_attribute swap_readahead_total_attr =
__ATTR(ra_total, 0444, swap_readahead_total_show, NULL);

+static ssize_t vma_ra_enabled_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%s\n", swap_vma_readahead ? "true" : "false");
+}
+static ssize_t vma_ra_enabled_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ if (!strncmp(buf, "true", 4) || !strncmp(buf, "1", 1))
+ swap_vma_readahead = true;
+ else if (!strncmp(buf, "false", 5) || !strncmp(buf, "0", 1))
+ swap_vma_readahead = false;
+ else
+ return -EINVAL;
+
+ return count;
+}
+static struct kobj_attribute vma_ra_enabled_attr =
+ __ATTR(vma_ra_enabled, 0644, vma_ra_enabled_show,
+ vma_ra_enabled_store);
+
+static ssize_t vma_ra_max_order_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%d\n", swap_ra_max_order);
+}
+static ssize_t vma_ra_max_order_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ int err, v;
+
+ err = kstrtoint(buf, 10, &v);
+ if (err || v > SWAP_RA_ORDER_CEILING || v <= 0)
+ return -EINVAL;
+
+ swap_ra_max_order = v;
+
+ return count;
+}
+static struct kobj_attribute vma_ra_max_order_attr =
+ __ATTR(vma_ra_max_order, 0644, vma_ra_max_order_show,
+ vma_ra_max_order_store);
+
static struct attribute *swap_attrs[] = {
&swap_cache_pages_attr.attr,
&swap_cache_add_attr.attr,
@@ -820,6 +865,8 @@ static struct attribute *swap_attrs[] = {
&swap_cache_find_total_attr.attr,
&swap_readahead_hits_attr.attr,
&swap_readahead_total_attr.attr,
+ &vma_ra_enabled_attr.attr,
+ &vma_ra_max_order_attr.attr,
NULL,
};

--
2.11.0