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

[Huang, Ying]

From: Huang Ying <ying.hu...@intel.com>

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.hu...@intel.com>
Cc: Minchan Kim <minc...@kernel.org>
Cc: Rik van Riel <r...@redhat.com>
Cc: Shaohua Li <s...@kernel.org>
Cc: Hugh Dickins <hu...@google.com>
Cc: Fengguang Wu <fengguang...@intel.com>
Cc: Tim Chen <tim.c.c...@intel.com>
Cc: Dave Hansen <dave.han...@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