[PATCH] vmalloc stats in /proc/meminfo

From: Matt Porter <porter@cox.net>

There was a thread a while back on lkml where Dave Hansen proposed this
simple vmalloc usage reporting patch.  The thread pretty much died out as
most people seemed focused on what VM loading type bugs it could solve.  I
had posted that this type of information was really valuable in debugging
embedded Linux board ports.  A common example is where people do arch
specific setup that limits there vmalloc space and then they find modules
won't load.  ;) Having the Vmalloc* info readily available is real useful in
helping folks to fix their kernel ports.

fs/proc/proc_misc.c

@@ -43,6 +43,7 @@
 #include <linux/hugetlb.h>
 #include <linux/jiffies.h>
 #include <linux/sysrq.h>
+#include <linux/vmalloc.h>
 #include <asm/uaccess.h>
 #include <asm/pgtable.h>
 #include <asm/io.h>
@@ -98,6 +99,41 @@ static int loadavg_read_proc(char *page, char **start, off_t off,
 	return proc_calc_metrics(page, start, off, count, eof, len);
 }
 
+struct vmalloc_info {
+	unsigned long used;
+	unsigned long largest_chunk;
+};
+
+static struct vmalloc_info get_vmalloc_info(void)
+{
+	unsigned long prev_end = VMALLOC_START;
+	struct vm_struct* vma;
+	struct vmalloc_info vmi;
+	vmi.used = 0;
+
+	read_lock(&vmlist_lock);
+
+	if(!vmlist)
+		vmi.largest_chunk = (VMALLOC_END-VMALLOC_START);
+	else
+		vmi.largest_chunk = 0;
+
+	for (vma = vmlist; vma; vma = vma->next) {
+		unsigned long free_area_size =
+			(unsigned long)vma->addr - prev_end;
+		vmi.used += vma->size;
+		if (vmi.largest_chunk < free_area_size )
+
+			vmi.largest_chunk = free_area_size;
+		prev_end = vma->size + (unsigned long)vma->addr;
+	}
+	if(VMALLOC_END-prev_end > vmi.largest_chunk)
+		vmi.largest_chunk = VMALLOC_END-prev_end;
+
+	read_unlock(&vmlist_lock);
+	return vmi;
+}
+
 static int uptime_read_proc(char *page, char **start, off_t off,
 				 int count, int *eof, void *data)
 {
@@ -143,6 +179,8 @@ static int meminfo_read_proc(char *page, char **start, off_t off,
 	unsigned long inactive;
 	unsigned long active;
 	unsigned long free;
+	unsigned long vmtot;
+	struct vmalloc_info vmi;
 
 	get_page_state(&ps);
 	get_zone_counts(&active, &inactive, &free);
@@ -155,6 +193,11 @@ static int meminfo_read_proc(char *page, char **start, off_t off,
 	si_swapinfo(&i);
 	committed = atomic_read(&vm_committed_space);
 
+	vmtot = (VMALLOC_END-VMALLOC_START)>>10;
+	vmi = get_vmalloc_info();
+	vmi.used >>= 10;
+	vmi.largest_chunk >>= 10;
+
 	/*
 	 * Tagged format, for easy grepping and expansion.
 	 */
@@ -177,7 +220,10 @@ static int meminfo_read_proc(char *page, char **start, off_t off,
 		"Mapped:       %8lu kB\n"
 		"Slab:         %8lu kB\n"
 		"Committed_AS: %8u kB\n"
-		"PageTables:   %8lu kB\n",
+		"PageTables:   %8lu kB\n"
+		"VmallocTotal: %8lu kB\n"
+		"VmallocUsed:  %8lu kB\n"
+		"VmallocChunk: %8lu kB\n",
 		K(i.totalram),
 		K(i.freeram),
 		K(i.bufferram),
@@ -196,7 +242,10 @@ static int meminfo_read_proc(char *page, char **start, off_t off,
 		K(ps.nr_mapped),
 		K(ps.nr_slab),
 		K(committed),
-		K(ps.nr_page_table_pages)
+		K(ps.nr_page_table_pages),
+		vmtot,
+		vmi.used,
+		vmi.largest_chunk
 		);
 
 		len += hugetlb_report_meminfo(page + len);