3 files changed, 14 insertions, 13 deletions
diff --git a/Documentation/vm/ksm.txt b/Documentation/vm/ksm.txt
index 72a22f65960e..262d8e6793a3 100644
@@ -52,15 +52,15 @@ The KSM daemon is controlled by sysfs files in /sys/kernel/mm/ksm/,
readable by all but writable only by root:
max_kernel_pages - set to maximum number of kernel pages that KSM may use
- e.g. "echo 2000 > /sys/kernel/mm/ksm/max_kernel_pages"
+ e.g. "echo 100000 > /sys/kernel/mm/ksm/max_kernel_pages"
Value 0 imposes no limit on the kernel pages KSM may use;
but note that any process using MADV_MERGEABLE can cause
KSM to allocate these pages, unswappable until it exits.
- Default: 2000 (chosen for demonstration purposes)
+ Default: quarter of memory (chosen to not pin too much)
pages_to_scan - how many present pages to scan before ksmd goes to sleep
- e.g. "echo 200 > /sys/kernel/mm/ksm/pages_to_scan"
- Default: 200 (chosen for demonstration purposes)
+ e.g. "echo 100 > /sys/kernel/mm/ksm/pages_to_scan"
+ Default: 100 (chosen for demonstration purposes)
sleep_millisecs - how many milliseconds ksmd should sleep before next scan
e.g. "echo 20 > /sys/kernel/mm/ksm/sleep_millisecs"
@@ -70,7 +70,8 @@ run - set 0 to stop ksmd from running but keep merged pages,
set 1 to run ksmd e.g. "echo 1 > /sys/kernel/mm/ksm/run",
set 2 to stop ksmd and unmerge all pages currently merged,
but leave mergeable areas registered for next run
- Default: 1 (for immediate use by apps which register)
+ Default: 0 (must be changed to 1 to activate KSM,
+ except if CONFIG_SYSFS is disabled)
The effectiveness of KSM and MADV_MERGEABLE is shown in /sys/kernel/mm/ksm/:
@@ -86,4 +87,4 @@ pages_volatile embraces several different kinds of activity, but a high
proportion there would also indicate poor use of madvise MADV_MERGEABLE.
-Hugh Dickins, 30 July 2009
+Hugh Dickins, 24 Sept 2009
diff --git a/mm/Kconfig b/mm/Kconfig
index edd300aca173..57963c6063d1 100644
@@ -224,7 +224,9 @@ config KSM
the many instances by a single resident 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.
+ See Documentation/vm/ksm.txt for more information: KSM is inactive
+ until a program has madvised that an area is MADV_MERGEABLE, and
+ root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
int "Low address space to protect from user allocation"
@@ -184,11 +184,6 @@ static DEFINE_SPINLOCK(ksm_mmlist_lock);
sizeof(struct __struct), __alignof__(struct __struct),\
-static void __init ksm_init_max_kernel_pages(void)
- ksm_max_kernel_pages = nr_free_buffer_pages() / 4;
static int __init ksm_slab_init(void)
rmap_item_cache = KSM_KMEM_CACHE(rmap_item, 0);
@@ -1673,7 +1668,7 @@ static int __init ksm_init(void)
struct task_struct *ksm_thread;
+ ksm_max_kernel_pages = totalram_pages / 4;
err = ksm_slab_init();
@@ -1697,6 +1692,9 @@ static int __init ksm_init(void)
+ ksm_run = KSM_RUN_MERGE; /* no way for user to start it */
#endif /* CONFIG_SYSFS */