| author | Hugh Dickins
<hugh.dickins@tiscali.co.uk> 2009-10-07 23:32:22 UTC |
| committer | Linus Torvalds
<torvalds@linux-foundation.org> 2009-10-08 14:36:38 UTC |
| parent | 0eca52a92735f43462165efe00a7e394345fb38e |
| Documentation/vm/ksm.txt | +7 | -6 |
| mm/Kconfig | +3 | -1 |
| mm/ksm.c | +4 | -6 |
diff --git a/Documentation/vm/ksm.txt b/Documentation/vm/ksm.txt index 72a22f65960..262d8e6793a 100644 --- a/Documentation/vm/ksm.txt +++ b/Documentation/vm/ksm.txt @@ -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. Izik Eidus, -Hugh Dickins, 30 July 2009 +Hugh Dickins, 24 Sept 2009 diff --git a/mm/Kconfig b/mm/Kconfig index edd300aca17..57963c6063d 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -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). config DEFAULT_MMAP_MIN_ADDR int "Low address space to protect from user allocation" diff --git a/mm/ksm.c b/mm/ksm.c index f7edac356f4..bef1af4f77e 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -184,11 +184,6 @@ static DEFINE_SPINLOCK(ksm_mmlist_lock); sizeof(struct __struct), __alignof__(struct __struct),\ (__flags), NULL) -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; int err; - ksm_init_max_kernel_pages(); + ksm_max_kernel_pages = totalram_pages / 4; err = ksm_slab_init(); if (err) @@ -1697,6 +1692,9 @@ static int __init ksm_init(void) kthread_stop(ksm_thread); goto out_free2; } +#else + ksm_run = KSM_RUN_MERGE; /* no way for user to start it */ + #endif /* CONFIG_SYSFS */ return 0;