[PATCH] usemem: Add option touch-alloc

[Hui Zhu]

Some environment will not fault in memory even if MAP_POPULATE is set.
This commit add option touch-alloc to read memory after allocate it to
make sure the pages is fault in.

Signed-off-by: Hui Zhu <teawat...@linux.alibaba.com>
---
 usemem.c | 37 +++++++++++++++++++++++++------------
 1 file changed, 25 insertions(+), 12 deletions(-)

diff --git a/usemem.c b/usemem.c
index 6d1d575..d93691b 100644
--- a/usemem.c
+++ b/usemem.c
@@ -97,6 +97,7 @@ unsigned long opt_delay = 0;
 int opt_read_again = 0;
 int opt_punch_holes = 0;
 int opt_init_time = 0;
+int opt_touch_alloc = 0;
 int nr_task;
 int nr_thread;
 int nr_cpu;
@@ -157,6 +158,7 @@ void usage(int ok)
        "    -Z|--read-again     read memory again after access the memory\n"
        "    --punch-holes       free every other page after allocation\n"
        "    --init-time         remove the initialization time from the run 
time and show the initialization time\n"
+       "    --touch-alloc       read memory after allocate it\n"
        "    -h|--help           show this message\n"
        ,               ourname);
 
@@ -197,6 +199,7 @@ static const struct option opts[] = {
        { "read-again"  , 0, NULL, 'Z' },
        { "punch-holes" , 0, NULL,   0 },
        { "init-time"   , 0, NULL,   0 },
+       { "touch-alloc" , 0, NULL,   0 },
        { "help"        , 0, NULL, 'h' },
        { NULL          , 0, NULL, 0 }
 };
@@ -326,6 +329,18 @@ void detach(void)
        }
 }
 
+unsigned long do_access(unsigned long *p, unsigned long idx, int read)
+{
+       volatile unsigned long *vp = p;
+
+       if (read)
+               return vp[idx]; /* read data */
+       else {
+               vp[idx] = idx;  /* write data */
+               return 0;
+       }
+}
+
 unsigned long * allocate(unsigned long bytes)
 {
        unsigned long *p;
@@ -352,6 +367,14 @@ unsigned long * allocate(unsigned long bytes)
                p = (unsigned long *)ALIGN((unsigned long)p, pagesize - 1);
        }
 
+       if (opt_touch_alloc) {
+               unsigned long i;
+               unsigned long m = bytes / sizeof(*p);
+
+               for (i = 0; i < m; i += 1)
+                       do_access(p, i, 1);
+       }
+
        return p;
 }
 
@@ -433,18 +456,6 @@ void shm_unlock(int seg_id)
        shmctl(seg_id, SHM_UNLOCK, NULL);
 }
 
-unsigned long do_access(unsigned long *p, unsigned long idx, int read)
-{
-       volatile unsigned long *vp = p;
-
-       if (read)
-               return vp[idx]; /* read data */
-       else {
-               vp[idx] = idx;  /* write data */
-               return 0;
-       }
-}
-
 #define NSEC_PER_SEC  (1UL * 1000 * 1000 * 1000)
 
 long nsec_sub(long nsec1, long nsec2)
@@ -950,6 +961,8 @@ int main(int argc, char *argv[])
                                opt_punch_holes = 1;
                        } else if (strcmp(opts[opt_index].name, "init-time") == 
0) { 
                                opt_init_time = 1;
+                       } else if (strcmp(opts[opt_index].name, "touch-alloc") 
== 0) { 
+                               opt_touch_alloc = 1;
                        } else
                                usage(1);
                        break;
-- 
2.17.1