From: Huang Ying <ying.huang@xxxxxxxxx>
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.
The corresponding ABI documentation is added too.
Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Shaohua Li <shli@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Fengguang Wu <fengguang.wu@xxxxxxxxx>
Cc: Tim Chen <tim.c.chen@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
---
Documentation/ABI/testing/sysfs-kernel-mm-swap | 26 +++++++++
mm/swap_state.c | 80 ++++++++++++++++++++++++++
2 files changed, 106 insertions(+)
create mode 100644 Documentation/ABI/testing/sysfs-kernel-mm-swap
diff --git a/Documentation/ABI/testing/sysfs-kernel-mm-swap b/Documentation/ABI/testing/sysfs-kernel-mm-swap
new file mode 100644
index 000000000000..587db52084c7
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-kernel-mm-swap
@@ -0,0 +1,26 @@
+What: /sys/kernel/mm/swap/
+Date: August 2017
+Contact: Linux memory management mailing list <linux-mm@xxxxxxxxx>
+Description: Interface for swapping
+
+What: /sys/kernel/mm/swap/vma_ra_enabled
+Date: August 2017
+Contact: Linux memory management mailing list <linux-mm@xxxxxxxxx>
+Description: Enable/disable VMA based swap readahead.
+
+ If set to true, the VMA based swap readahead algorithm
+ will be used for swappable anonymous pages mapped in a
+ VMA, and the global swap readahead algorithm will be
+ still used for tmpfs etc. other users. If set to
+ false, the global swap readahead algorithm will be
+ used for all swappable pages.
+
+What: /sys/kernel/mm/swap/vma_ra_max_order
+Date: August 2017
+Contact: Linux memory management mailing list <linux-mm@xxxxxxxxx>
+Description: The max readahead size in order for VMA based swap readahead
+
+ VMA based swap readahead algorithm will readahead at
+ most 1 << max_order pages for each readahead. The
+ real readahead size for each readahead will be scaled
+ according to the estimation algorithm.
diff --git a/mm/swap_state.c b/mm/swap_state.c
index 3885fef7bdf5..71ce2d1ccbf7 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -751,3 +751,83 @@ struct page *do_swap_page_readahead(swp_entry_t fentry, gfp_t gfp_mask,
return read_swap_cache_async(fentry, gfp_mask, vma, vmf->address,
swap_ra->win == 1);
}
+
+#ifdef CONFIG_SYSFS
+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[] = {
+ &vma_ra_enabled_attr.attr,
+ &vma_ra_max_order_attr.attr,
+ NULL,
+};
+
+static struct attribute_group swap_attr_group = {
+ .attrs = swap_attrs,
+};
+
+static int __init swap_init_sysfs(void)
+{
+ int err;
+ struct kobject *swap_kobj;
+
+ swap_kobj = kobject_create_and_add("swap", mm_kobj);
+ if (!swap_kobj) {
+ pr_err("failed to create swap kobject\n");
+ return -ENOMEM;
+ }
+ err = sysfs_create_group(swap_kobj, &swap_attr_group);
+ if (err) {
+ pr_err("failed to register swap group\n");
+ goto delete_obj;
+ }
+ return 0;
+
+delete_obj:
+ kobject_put(swap_kobj);
+ return err;
+}
+subsys_initcall(swap_init_sysfs);
+#endif
--
2.11.0
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