On 11/04/2015 08:40 PM, Eduardo Habkost wrote:
On Wed, Nov 04, 2015 at 11:12:41AM +0800, Xiao Guangrong wrote:
On 11/04/2015 07:00 AM, Eduardo Habkost wrote:
On Mon, Nov 02, 2015 at 05:13:10PM +0800, Xiao Guangrong wrote:
Currently file_ram_alloc() is designed for hugetlbfs, however, the memory
of nvdimm can come from either raw pmem device eg, /dev/pmem, or the file
locates at DAX enabled filesystem

So this patch let it work on any kind of path

Signed-off-by: Xiao Guangrong <guangrong.x...@linux.intel.com>
  exec.c | 24 ++++++++++++------------
  1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/exec.c b/exec.c
index 9de38be..9075f4d 100644
--- a/exec.c
+++ b/exec.c
@@ -1184,25 +1184,25 @@ static void *file_ram_alloc(RAMBlock *block,
      char *c;
      void *area;
      int fd;
-    uint64_t hpagesize;
+    uint64_t pagesize;
      Error *local_err = NULL;

-    hpagesize = qemu_file_get_page_size(path, &local_err);
+    pagesize = qemu_file_get_page_size(path, &local_err);
      if (local_err) {
          error_propagate(errp, local_err);
          goto error;

-    if (hpagesize == getpagesize()) {
-        fprintf(stderr, "Warning: path not on HugeTLBFS: %s\n", path);
+    if (pagesize == getpagesize()) {
+        fprintf(stderr, "Memory is not allocated from HugeTlbfs.\n");

If the point of this patch is to allow file_ram_alloc() to not be
specific to hugetlbfs anymore, this warning can simply go away.

(And in case if you really want to keep the warning, I don't see the
point of the changes you made to it.)

This is the history why we did it like this:

The rule I am trying to follow is simple: if there are valid use cases
(e.g. nvdimm, tmpfs) where the warning will be printed every single time
QEMU runs, the warning is not appropriate.

If you really want to keep a warning, please make it not be printed on
all other valid use cases (nvdimm and tmpfs). Personally, I don't think
adding those additional checks would be worth the trouble, that's why I
suggest removing the warning.

| What this *actually* is trying to warn against is that
| mapping a regular file (as opposed to hugetlbfs)
| means transparent huge pages don't work.

I don't think the author of that warning even thought about transparent
huge pages (did THP even existed when it was written?). I believe they
just assumed that the only reason for using -mem-path would be hugetlbfs
and wanted to warn about it. That assumption isn't true anymore.

Michael, your idea?

If Michael will not beat me, i will drop this. :)
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