Commit 2ffd8679 authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
Browse files

ksm: sysfs and defaults

At present KSM is just a waste of space if you don't have CONFIG_SYSFS=y
to provide the /sys/kernel/mm/ksm files to tune and activate it.

Make KSM depend on SYSFS?  Could do, but it might be better to provide
some defaults so that KSM works out-of-the-box, ready for testers to
madvise MADV_MERGEABLE, even without SYSFS.

Though anyone serious is likely to want to retune the numbers to their
taste once they have experience; and whether these settings ever reach
2.6.32 can be discussed along the way.

Save 1kB from tiny kernels by #ifdef'ing the SYSFS side of it.
Signed-off-by: default avatarHugh Dickins <>
Acked-by: default avatarIzik Eidus <>
Cc: Andrea Arcangeli <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 1c2fb7a4
......@@ -163,18 +163,18 @@ static unsigned long ksm_pages_unshared;
static unsigned long ksm_rmap_items;
/* Limit on the number of unswappable pages used */
static unsigned long ksm_max_kernel_pages;
static unsigned long ksm_max_kernel_pages = 2000;
/* Number of pages ksmd should scan in one batch */
static unsigned int ksm_thread_pages_to_scan;
static unsigned int ksm_thread_pages_to_scan = 200;
/* Milliseconds ksmd should sleep between batches */
static unsigned int ksm_thread_sleep_millisecs;
static unsigned int ksm_thread_sleep_millisecs = 20;
#define KSM_RUN_STOP 0
#define KSM_RUN_MERGE 1
static unsigned int ksm_run;
static unsigned int ksm_run = KSM_RUN_MERGE;
static DECLARE_WAIT_QUEUE_HEAD(ksm_thread_wait);
static DEFINE_MUTEX(ksm_thread_mutex);
......@@ -506,6 +506,10 @@ static int unmerge_ksm_pages(struct vm_area_struct *vma,
return err;
* Only called through the sysfs control interface:
static int unmerge_and_remove_all_rmap_items(void)
struct mm_slot *mm_slot;
......@@ -563,6 +567,7 @@ error:
return err;
#endif /* CONFIG_SYSFS */
static u32 calc_checksum(struct page *page)
......@@ -1454,6 +1459,11 @@ void __ksm_exit(struct mm_struct *mm)
* This all compiles without CONFIG_SYSFS, but is a waste of space.
#define KSM_ATTR_RO(_name) \
static struct kobj_attribute _name##_attr = __ATTR_RO(_name)
#define KSM_ATTR(_name) \
......@@ -1636,6 +1646,7 @@ static struct attribute_group ksm_attr_group = {
.attrs = ksm_attrs,
.name = "ksm",
#endif /* CONFIG_SYSFS */
static int __init ksm_init(void)
......@@ -1657,16 +1668,17 @@ static int __init ksm_init(void)
goto out_free2;
err = sysfs_create_group(mm_kobj, &ksm_attr_group);
if (err) {
printk(KERN_ERR "ksm: register sysfs failed\n");
goto out_free3;
goto out_free2;
#endif /* CONFIG_SYSFS */
return 0;
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment