util/oslib-posix: Avoid creating a single thread with MADV_POPULATE_WRITE

Let's simplify the case when we only want a single thread and don't have
to mess with signal handlers.

Reviewed-by: Pankaj Gupta <pankaj.gupta@ionos.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20211217134611.31172-6-david@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/util/oslib-posix.c b/util/oslib-posix.c
index 67c08a4..efa4f96 100644
--- a/util/oslib-posix.c
+++ b/util/oslib-posix.c
@@ -564,6 +564,14 @@ static int touch_all_pages(char *area, size_t hpagesize, size_t numpages,
     }
 
     if (use_madv_populate_write) {
+        /* Avoid creating a single thread for MADV_POPULATE_WRITE */
+        if (context.num_threads == 1) {
+            if (qemu_madvise(area, hpagesize * numpages,
+                             QEMU_MADV_POPULATE_WRITE)) {
+                return -errno;
+            }
+            return 0;
+        }
         touch_fn = do_madv_populate_write_pages;
     } else {
         touch_fn = do_touch_pages;