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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 <hugh.dickins@tiscali.co.uk>
Acked-by: default avatarIzik Eidus <ieidus@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 1c2fb7a4

mm/ksm.c

+19 −7
Original line number Diff line number Diff line
@@ -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

#define KSM_RUN_UNMERGE	2

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;

}



#ifdef CONFIG_SYSFS

/*

 * 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 @@ static int unmerge_and_remove_all_rmap_items(void) 
	spin_unlock(&ksm_mmlist_lock);

	return err;

}

#endif /* CONFIG_SYSFS */



static u32 calc_checksum(struct page *page)

{
@@ -1454,6 +1459,11 @@ void __ksm_exit(struct mm_struct *mm) 
	}

}



#ifdef CONFIG_SYSFS

/*

 * 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;

	}



#ifdef CONFIG_SYSFS

	err = sysfs_create_group(mm_kobj, &ksm_attr_group);

	if (err) {

		printk(KERN_ERR "ksm: register sysfs failed\n");

		goto out_free3;

		kthread_stop(ksm_thread);

		goto out_free2;

	}

#endif /* CONFIG_SYSFS */



	return 0;



out_free3:

	kthread_stop(ksm_thread);

out_free2:

	mm_slots_hash_free();

out_free1: