[PATCH] proc/meminfo: add MemKernel counter

[Konstantin Khlebnikov]

Some kinds of kernel allocations are not accounted or not show in meminfo.
For example vmalloc allocations are tracked but overall size is not shown
for performance reasons. There is no information about network buffers.

In most cases detailed statistics is not required. At first place we need
information about overall kernel memory usage regardless of its structure.

This patch estimates kernel memory usage by subtracting known sizes of
free, anonymous, hugetlb and caches from total memory size: MemKernel =
MemTotal - MemFree - Buffers - Cached - SwapCached - AnonPages - Hugetlb.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
---
 Documentation/filesystems/proc.txt |    5 +++++
 fs/proc/meminfo.c                  |   20 +++++++++++++++-----
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index 66cad5c86171..a0ab7f273ea0 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -860,6 +860,7 @@ varies by architecture and compile options.  The following is from a
 
 MemTotal:     16344972 kB
 MemFree:      13634064 kB
+MemKernel:      862600 kB
 MemAvailable: 14836172 kB
 Buffers:          3656 kB
 Cached:        1195708 kB
@@ -908,6 +909,10 @@ MemAvailable: An estimate of how much memory is available for starting new
               page cache to function well, and that not all reclaimable
               slab will be reclaimable, due to items being in use. The
               impact of those factors will vary from system to system.
+   MemKernel: The sum of all kinds of kernel memory allocations: Slab,
+              Vmalloc, Percpu, KernelStack, PageTables, socket buffers,
+              and some other untracked allocations. Does not include
+              MemFree, Buffers, Cached, SwapCached, AnonPages, Hugetlb.
      Buffers: Relatively temporary storage for raw disk blocks
               shouldn't get tremendously large (20MB or so)
       Cached: in-memory cache for files read from the disk (the
diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
index 568d90e17c17..b27d56dd619a 100644
--- a/fs/proc/meminfo.c
+++ b/fs/proc/meminfo.c
@@ -39,17 +39,27 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
 	long available;
 	unsigned long pages[NR_LRU_LISTS];
 	unsigned long sreclaimable, sunreclaim;
+	unsigned long anon_pages, file_pages, swap_cached;
+	long kernel_pages;
 	int lru;
 
 	si_meminfo(&i);
 	si_swapinfo(&i);
 	committed = percpu_counter_read_positive(&vm_committed_as);
 
-	cached = global_node_page_state(NR_FILE_PAGES) -
-			total_swapcache_pages() - i.bufferram;
+	anon_pages = global_node_page_state(NR_ANON_MAPPED);
+	file_pages = global_node_page_state(NR_FILE_PAGES);
+	swap_cached = total_swapcache_pages();
+
+	cached = file_pages - swap_cached - i.bufferram;
 	if (cached < 0)
 		cached = 0;
 
+	kernel_pages = i.totalram - i.freeram - anon_pages - file_pages -
+		       hugetlb_total_pages();
+	if (kernel_pages < 0)
+		kernel_pages = 0;
+
 	for (lru = LRU_BASE; lru < NR_LRU_LISTS; lru++)
 		pages[lru] = global_node_page_state(NR_LRU_BASE + lru);
 
@@ -60,9 +70,10 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
 	show_val_kb(m, "MemTotal:       ", i.totalram);
 	show_val_kb(m, "MemFree:        ", i.freeram);
 	show_val_kb(m, "MemAvailable:   ", available);
+	show_val_kb(m, "MemKernel:      ", kernel_pages);
 	show_val_kb(m, "Buffers:        ", i.bufferram);
 	show_val_kb(m, "Cached:         ", cached);
-	show_val_kb(m, "SwapCached:     ", total_swapcache_pages());
+	show_val_kb(m, "SwapCached:     ", swap_cached);
 	show_val_kb(m, "Active:         ", pages[LRU_ACTIVE_ANON] +
 					   pages[LRU_ACTIVE_FILE]);
 	show_val_kb(m, "Inactive:       ", pages[LRU_INACTIVE_ANON] +
@@ -92,8 +103,7 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
 		    global_node_page_state(NR_FILE_DIRTY));
 	show_val_kb(m, "Writeback:      ",
 		    global_node_page_state(NR_WRITEBACK));
-	show_val_kb(m, "AnonPages:      ",
-		    global_node_page_state(NR_ANON_MAPPED));
+	show_val_kb(m, "AnonPages:      ", anon_pages);
 	show_val_kb(m, "Mapped:         ",
 		    global_node_page_state(NR_FILE_MAPPED));
 	show_val_kb(m, "Shmem:          ", i.sharedram);