mm/page_alloc.c: calculate 'available' memory in a separate function

Add a new field, VIRTIO_BALLOON_S_AVAIL, to virtio_balloon memory
statistics protocol, corresponding to 'Available' in /proc/meminfo.

It indicates to the hypervisor how big the balloon can be inflated
without pushing the guest system to swap.  This metric would be very
useful in VM orchestration software to improve memory management of
different VMs under overcommit.

This patch (of 2):

Factor out calculation of the available memory counter into a separate
exportable function, in order to be able to use it in other parts of the
kernel.

In particular, it appears a relevant metric to report to the hypervisor
via virtio-balloon statistics interface (in a followup patch).

Signed-off-by: Igor Redko <redkoi@virtuozzo.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
index df4661abadc40fa406f9b36c3dfd344179e90eb8..83720460c5bc74c51a9caae002495b4d59d8a4c3 100644 (file)
--- a/fs/proc/meminfo.c
+++ b/fs/proc/meminfo.c
@@ -29,10 +29,7 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
        unsigned long committed;
        long cached;
        long available;
-       unsigned long pagecache;
-       unsigned long wmark_low = 0;
        unsigned long pages[NR_LRU_LISTS];
-       struct zone *zone;
        int lru;
 
 /*
@@ -51,33 +48,7 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
        for (lru = LRU_BASE; lru < NR_LRU_LISTS; lru++)
                pages[lru] = global_page_state(NR_LRU_BASE + lru);
 
-       for_each_zone(zone)
-               wmark_low += zone->watermark[WMARK_LOW];
-
-       /*
-        * Estimate the amount of memory available for userspace allocations,
-        * without causing swapping.
-        */
-       available = i.freeram - totalreserve_pages;
-
-       /*
-        * Not all the page cache can be freed, otherwise the system will
-        * start swapping. Assume at least half of the page cache, or the
-        * low watermark worth of cache, needs to stay.
-        */
-       pagecache = pages[LRU_ACTIVE_FILE] + pages[LRU_INACTIVE_FILE];
-       pagecache -= min(pagecache / 2, wmark_low);
-       available += pagecache;
-
-       /*
-        * Part of the reclaimable slab consists of items that are in use,
-        * and cannot be freed. Cap this estimate at the low watermark.
-        */
-       available += global_page_state(NR_SLAB_RECLAIMABLE) -
-                    min(global_page_state(NR_SLAB_RECLAIMABLE) / 2, wmark_low);
-
-       if (available < 0)
-               available = 0;
+       available = si_mem_available();
 
        /*
         * Tagged format, for easy grepping and expansion.

diff --git a/include/linux/mm.h b/include/linux/mm.h
index b3202612bb95b7c5d4def84b704c102aa9649642..db9df3f78de11d7ad8d9049c2383c07eee44fd00 100644 (file)
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1875,6 +1875,7 @@ extern int __meminit init_per_zone_wmark_min(void);
 extern void mem_init(void);
 extern void __init mmap_init(void);
 extern void show_mem(unsigned int flags);
+extern long si_mem_available(void);
 extern void si_meminfo(struct sysinfo * val);
 extern void si_meminfo_node(struct sysinfo *val, int nid);
 

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 25a75da53c2754837c978c21753c6d4f0c46539f..941b802e11ec1b1c0f7540a550982a215e59c8aa 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3713,6 +3713,49 @@ static inline void show_node(struct zone *zone)
                printk("Node %d ", zone_to_nid(zone));
 }
 
+long si_mem_available(void)
+{
+       long available;
+       unsigned long pagecache;
+       unsigned long wmark_low = 0;
+       unsigned long pages[NR_LRU_LISTS];
+       struct zone *zone;
+       int lru;
+
+       for (lru = LRU_BASE; lru < NR_LRU_LISTS; lru++)
+               pages[lru] = global_page_state(NR_LRU_BASE + lru);
+
+       for_each_zone(zone)
+               wmark_low += zone->watermark[WMARK_LOW];
+
+       /*
+        * Estimate the amount of memory available for userspace allocations,
+        * without causing swapping.
+        */
+       available = global_page_state(NR_FREE_PAGES) - totalreserve_pages;
+
+       /*
+        * Not all the page cache can be freed, otherwise the system will
+        * start swapping. Assume at least half of the page cache, or the
+        * low watermark worth of cache, needs to stay.
+        */
+       pagecache = pages[LRU_ACTIVE_FILE] + pages[LRU_INACTIVE_FILE];
+       pagecache -= min(pagecache / 2, wmark_low);
+       available += pagecache;
+
+       /*
+        * Part of the reclaimable slab consists of items that are in use,
+        * and cannot be freed. Cap this estimate at the low watermark.
+        */
+       available += global_page_state(NR_SLAB_RECLAIMABLE) -
+                    min(global_page_state(NR_SLAB_RECLAIMABLE) / 2, wmark_low);
+
+       if (available < 0)
+               available = 0;
+       return available;
+}
+EXPORT_SYMBOL_GPL(si_mem_available);
+
 void si_meminfo(struct sysinfo *val)
 {
        val->totalram = totalram_pages;