[PATCH v1 5/8] util/oslib-posix: Avoid creating a single thread with MADV_POPULATE_WRITE

From: David Hildenbrand <david@redhat.com>
To: qemu-devel@nongnu.org
Cc: "Pankaj Gupta" <pankaj.gupta.linux@gmail.com>,
	"Gavin Shan" <gshan@redhat.com>,
	"Daniel P . Berrangé" <berrange@redhat.com>,
	"Eduardo Habkost" <ehabkost@redhat.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	"Michal Prívozník" <mprivozn@redhat.com>,
	"David Hildenbrand" <david@redhat.com>,
	"Dr . David Alan Gilbert" <dgilbert@redhat.com>,
	"Pankaj Gupta" <pankaj.gupta@ionos.com>,
	"Sebastien Boeuf" <sebastien.boeuf@intel.com>,
	"Igor Mammedov" <imammedo@redhat.com>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Hui Zhu" <teawater@gmail.com>
Subject: [PATCH v1 5/8] util/oslib-posix: Avoid creating a single thread with MADV_POPULATE_WRITE
Date: Tue, 30 Nov 2021 11:41:33 +0100	[thread overview]
Message-ID: <20211130104136.40927-6-david@redhat.com> (raw)
In-Reply-To: <20211130104136.40927-1-david@redhat.com>

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>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 util/oslib-posix.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/util/oslib-posix.c b/util/oslib-posix.c
index 67c08a425e..efa4f96d56 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;
-- 
2.31.1


