From: Stefan Hajnoczi <stefanha@redhat.com>
Date: Wed, 9 Jul 2014 08:05:48 +0000 (+0200)
Subject: virtio-blk: avoid g_slice_new0() for VirtIOBlockReq and VirtQueueElement
X-Git-Tag: qemu-xen-4.6.0-rc1~310^2~9
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=869d66af53d8e04709456c9cae5cca7c560d4b93;p=qemu-upstream-4.6-testing.git

virtio-blk: avoid g_slice_new0() for VirtIOBlockReq and VirtQueueElement

In commit de6c8042ec55da18702fa51f09072fcaa315edc3 ("virtio-blk: Avoid
zeroing every request structure") we avoided the 40 KB memset when
allocating VirtIOBlockReq.

The memset was reintroduced in commit
671ec3f056559f22a2531a91dce3a258b9b5eb8a ("virtio-blk: Convert
VirtIOBlockReq.elem to pointer").

It must be fixed again to avoid a performance regression.

Cc: Fam Zheng <famz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---

diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index aec314675..b06a56d94 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -31,9 +31,11 @@
 
 static VirtIOBlockReq *virtio_blk_alloc_request(VirtIOBlock *s)
 {
-    VirtIOBlockReq *req = g_slice_new0(VirtIOBlockReq);
+    VirtIOBlockReq *req = g_slice_new(VirtIOBlockReq);
     req->dev = s;
-    req->elem = g_slice_new0(VirtQueueElement);
+    req->qiov.size = 0;
+    req->next = NULL;
+    req->elem = g_slice_new(VirtQueueElement);
     return req;
 }