ksm: remove unswappable max_kernel_pages

Now that ksm pages are swappable, and the known holes plugged, remove
mention of unswappable kernel pages from KSM documentation and comments.

Remove the totalram_pages/4 initialization of max_kernel_pages.  In fact,
remove max_kernel_pages altogether - we can reinstate it if removal turns
out to break someone's script; but if we later want to limit KSM's memory
usage, limiting the stable nodes would not be an effective approach.

Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Izik Eidus <ieidus@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Chris Wright <chrisw@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 3 insertions, 40 deletions

diff --git a/mm/Kconfig b/mm/Kconfig
index d4b5fff6ea09..2310984591ed 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -212,7 +212,7 @@ config KSM
           Enable Kernel Samepage Merging: KSM periodically scans those areas
           of an application's address space that an app has advised may be
           mergeable.  When it finds pages of identical content, it replaces
-          the many instances by a single resident page with that content, so
+          the many instances by a single page with that content, so
           saving memory until one or another app needs to modify the content.
           Recommended for use with KVM, or with other duplicative applications.
           See Documentation/vm/ksm.txt for more information: KSM is inactive
diff --git a/mm/ksm.c b/mm/ksm.c
index d4c228a9d278..56a0da1f9979 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -179,9 +179,6 @@ static unsigned long ksm_pages_unshared;
 /* The number of rmap_items in use: to calculate pages_volatile */
 static unsigned long ksm_rmap_items;
 
-/* Limit on the number of unswappable pages used */
-static unsigned long ksm_max_kernel_pages;
-
 /* Number of pages ksmd should scan in one batch */
 static unsigned int ksm_thread_pages_to_scan = 100;
 
@@ -943,14 +940,6 @@ static struct page *try_to_merge_two_pages(struct rmap_item *rmap_item,
 {
         int err;
 
-        /*
-         * The number of nodes in the stable tree
-         * is the number of kernel pages that we hold.
-         */
-        if (ksm_max_kernel_pages &&
-            ksm_max_kernel_pages <= ksm_pages_shared)
-                return NULL;
-
         err = try_to_merge_with_ksm_page(rmap_item, page, NULL);
         if (!err) {
                 err = try_to_merge_with_ksm_page(tree_rmap_item,
@@ -1850,8 +1839,8 @@ static ssize_t run_store(struct kobject *kobj, struct kobj_attribute *attr,
         /*
          * KSM_RUN_MERGE sets ksmd running, and 0 stops it running.
          * KSM_RUN_UNMERGE stops it running and unmerges all rmap_items,
-         * breaking COW to free the unswappable pages_shared (but leaves
-         * mm_slots on the list for when ksmd may be set running again).
+         * breaking COW to free the pages_shared (but leaves mm_slots
+         * on the list for when ksmd may be set running again).
          */
 
         mutex_lock(&ksm_thread_mutex);
@@ -1876,29 +1865,6 @@ static ssize_t run_store(struct kobject *kobj, struct kobj_attribute *attr,
 }
 KSM_ATTR(run);
 
-static ssize_t max_kernel_pages_store(struct kobject *kobj,
-                                      struct kobj_attribute *attr,
-                                      const char *buf, size_t count)
-{
-        int err;
-        unsigned long nr_pages;
-
-        err = strict_strtoul(buf, 10, &nr_pages);
-        if (err)
-                return -EINVAL;
-
-        ksm_max_kernel_pages = nr_pages;
-
-        return count;
-}
-
-static ssize_t max_kernel_pages_show(struct kobject *kobj,
-                                     struct kobj_attribute *attr, char *buf)
-{
-        return sprintf(buf, "%lu\n", ksm_max_kernel_pages);
-}
-KSM_ATTR(max_kernel_pages);
-
 static ssize_t pages_shared_show(struct kobject *kobj,
                                  struct kobj_attribute *attr, char *buf)
 {
@@ -1948,7 +1914,6 @@ static struct attribute *ksm_attrs[] = {
         &sleep_millisecs_attr.attr,
         &pages_to_scan_attr.attr,
         &run_attr.attr,
-        &max_kernel_pages_attr.attr,
         &pages_shared_attr.attr,
         &pages_sharing_attr.attr,
         &pages_unshared_attr.attr,
@@ -1968,8 +1933,6 @@ static int __init ksm_init(void)
         struct task_struct *ksm_thread;
         int err;
 
-        ksm_max_kernel_pages = totalram_pages / 4;
-
         err = ksm_slab_init();
         if (err)
                 goto out;