ShmemFreeHoles will be freed under memory pressure, but are not included
in MemFree: they need to be added into MemAvailable, and wherever the
kernel calculates freeable pages; but in a few other places also.
There is certainly room for debate about those places: I've made my
selection (and kept some notes), you may come up with a different list.
I decided against max_sane_readahead(), because I suspect it's already
too much; and left drivers/staging/android/lowmemorykiller.c out for now.
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
---
fs/proc/meminfo.c | 6 ++++++
mm/mmap.c | 1 +
mm/page-writeback.c | 2 ++
mm/vmscan.c | 3 ++-
4 files changed, 11 insertions(+), 1 deletion(-)
--- thpfs.orig/fs/proc/meminfo.c 2015-02-20 19:33:51.488038441 -0800
+++ thpfs/fs/proc/meminfo.c 2015-02-20 19:33:56.528026917 -0800
@@ -76,6 +76,12 @@ static int meminfo_proc_show(struct seq_
available += pagecache;
/*
+ * Shmem freeholes help to keep huge pages intact, but contain
+ * no data, and can be shrunk whenever small pages are needed.
+ */
+ available += global_page_state(NR_SHMEM_FREEHOLES);
+
+ /*
* Part of the reclaimable slab consists of items that are in use,
* and cannot be freed. Cap this estimate at the low watermark.
*/
--- thpfs.orig/mm/mmap.c 2015-02-08 18:54:22.000000000 -0800
+++ thpfs/mm/mmap.c 2015-02-20 19:33:56.528026917 -0800
@@ -168,6 +168,7 @@ int __vm_enough_memory(struct mm_struct
if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
free = global_page_state(NR_FREE_PAGES);
+ free += global_page_state(NR_SHMEM_FREEHOLES);
free += global_page_state(NR_FILE_PAGES);
/*
--- thpfs.orig/mm/page-writeback.c 2015-02-08 18:54:22.000000000 -0800
+++ thpfs/mm/page-writeback.c 2015-02-20 19:33:56.532026908 -0800
@@ -187,6 +187,7 @@ static unsigned long zone_dirtyable_memo
nr_pages = zone_page_state(zone, NR_FREE_PAGES);
nr_pages -= min(nr_pages, zone->dirty_balance_reserve);
+ nr_pages += zone_page_state(zone, NR_SHMEM_FREEHOLES);
nr_pages += zone_page_state(zone, NR_INACTIVE_FILE);
nr_pages += zone_page_state(zone, NR_ACTIVE_FILE);
@@ -241,6 +242,7 @@ static unsigned long global_dirtyable_me
x = global_page_state(NR_FREE_PAGES);
x -= min(x, dirty_balance_reserve);
+ x += global_page_state(NR_SHMEM_FREEHOLES);
x += global_page_state(NR_INACTIVE_FILE);
x += global_page_state(NR_ACTIVE_FILE);
--- thpfs.orig/mm/vmscan.c 2015-02-20 19:33:31.056085158 -0800
+++ thpfs/mm/vmscan.c 2015-02-20 19:33:56.532026908 -0800
@@ -1946,7 +1946,8 @@ static void get_scan_count(struct lruvec
unsigned long zonefile;
unsigned long zonefree;
- zonefree = zone_page_state(zone, NR_FREE_PAGES);
+ zonefree = zone_page_state(zone, NR_FREE_PAGES) +
+ zone_page_state(zone, NR_SHMEM_FREEHOLES);
zonefile = zone_page_state(zone, NR_ACTIVE_FILE) +
zone_page_state(zone, NR_INACTIVE_FILE);
--
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