[1/2] kvm/qemu: use statfs to determine size of huge pages

Commit Message

Joerg Roedel March 27, 2009, 2:34 p.m. UTC

The current method of finding out the size of huge pages does not work
reliable anymore. Current Linux supports more than one huge page size
but /proc/meminfo only show one of the supported sizes.
To find out the real page size used can be found by calling statfs. This
patch changes kvm/qemu to use statfs instead of parsing /proc/meminfo.

Signed-off-by: Joerg Roedel <[e-mail]>
---
 qemu/sysemu.h |    2 +-
 qemu/vl.c     |   42 +++++++++++++++++++-----------------------
 2 files changed, 20 insertions(+), 24 deletions(-)

Comments

Avi Kivity March 29, 2009, 11:56 a.m. UTC | #1

Joerg Roedel wrote:
> The current method of finding out the size of huge pages does not work
> reliable anymore. Current Linux supports more than one huge page size
> but /proc/meminfo only show one of the supported sizes.
> To find out the real page size used can be found by calling statfs. This
> patch changes kvm/qemu to use statfs instead of parsing /proc/meminfo.
>   

Applied, thanks.

Patch

diff --git a/qemu/sysemu.h b/qemu/sysemu.h
index 4457a40..d765465 100644
--- a/qemu/sysemu.h
+++ b/qemu/sysemu.h
@@ -105,7 +105,7 @@  extern int graphic_rotate;
 extern int no_quit;
 extern int semihosting_enabled;
 extern int old_param;
-extern int hpagesize;
+extern long hpagesize;
 extern const char *bootp_filename;
 
 #ifdef USE_KQEMU
diff --git a/qemu/vl.c b/qemu/vl.c
index c52d2d7..f820d3a 100644
--- a/qemu/vl.c
+++ b/qemu/vl.c
@@ -42,6 +42,7 @@ 
 #include <sys/ioctl.h>
 #include <sys/resource.h>
 #include <sys/socket.h>
+#include <sys/vfs.h>
 #include <netinet/in.h>
 #include <net/if.h>
 #if defined(__NetBSD__)
@@ -261,7 +262,7 @@  const char *mem_path = NULL;
 #ifdef MAP_POPULATE
 int mem_prealloc = 1;	/* force preallocation of physical target memory */
 #endif
-int hpagesize = 0;
+long hpagesize = 0;
 const char *cpu_vendor_string;
 #ifdef TARGET_ARM
 int old_param = 0;
@@ -4747,32 +4748,27 @@  void qemu_get_launch_info(int *argc, char ***argv, int *opt_daemonize, const cha
 }
 
 #ifdef USE_KVM
-static int gethugepagesize(void)
+
+#define HUGETLBFS_MAGIC       0x958458f6
+
+static long gethugepagesize(const char *path)
 {
-    int ret, fd;
-    char buf[4096];
-    const char *needle = "Hugepagesize:";
-    char *size;
-    unsigned long hugepagesize;
+    struct statfs fs;
+    int ret;
 
-    fd = open("/proc/meminfo", O_RDONLY);
-    if (fd < 0) {
-	perror("open");
-	exit(0);
-    }
+    do {
+	    ret = statfs(path, &fs);
+    } while (ret != 0 && errno == EINTR);
 
-    ret = read(fd, buf, sizeof(buf));
-    if (ret < 0) {
-	perror("read");
-	exit(0);
+    if (ret != 0) {
+	    perror("statfs");
+	    return 0;
     }
 
-    size = strstr(buf, needle);
-    if (!size)
-	return 0;
-    size += strlen(needle);
-    hugepagesize = strtol(size, NULL, 0);
-    return hugepagesize;
+    if (fs.f_type != HUGETLBFS_MAGIC)
+	    fprintf(stderr, "Warning: path not on HugeTLBFS: %s\n", path);
+
+    return fs.f_bsize;
 }
 
 static void *alloc_mem_area(size_t memory, unsigned long *len, const char *path)
@@ -4792,7 +4788,7 @@  static void *alloc_mem_area(size_t memory, unsigned long *len, const char *path)
     if (asprintf(&filename, "%s/kvm.XXXXXX", path) == -1)
 	return NULL;
 
-    hpagesize = gethugepagesize() * 1024;
+    hpagesize = gethugepagesize(path);
     if (!hpagesize)
 	return NULL;