From c73602ad31cdcf7e6651f43d12f65b5b9b825b6f Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Wed, 7 Oct 2009 16:32:22 -0700 Subject: ksm: more on default values Adjust the max_kernel_pages default to a quarter of totalram_pages, instead of nr_free_buffer_pages() / 4: the KSM pages themselves come from highmem, and even on a 16GB PAE machine, 4GB of KSM pages would only be pinning 32MB of lowmem with their rmap_items, so no need for the more obscure calculation (nor for its own special init function). There is no way for the user to switch KSM on if CONFIG_SYSFS is not enabled, so in that case default run to KSM_RUN_MERGE. Update KSM Documentation and Kconfig to reflect the new defaults. Signed-off-by: Hugh Dickins Cc: Izik Eidus Cc: Andrea Arcangeli Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/vm/ksm.txt | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) (limited to 'Documentation') diff --git a/Documentation/vm/ksm.txt b/Documentation/vm/ksm.txt index 72a22f65960e..262d8e6793a3 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 -- cgit v1.2.3