Skip automatic zero-init of large arrays / structs in I/O paths

[PATCH 30/31] net/socket: skip automatic zero-init of large array

Daniel P. Berrangé posted 31 patches 5 months, 1 week ago

Download mbox

Maintainers: Kevin Wolf <kwolf@redhat.com>, Hanna Reitz <hreitz@redhat.com>, "Marc-André Lureau" <marcandre.lureau@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, Gerd Hoffmann <kraxel@redhat.com>, Halil Pasic <pasic@linux.ibm.com>, Christian Borntraeger <borntraeger@linux.ibm.com>, Thomas Huth <thuth@redhat.com>, Dmitry Fleytman <dmitry.fleytman@gmail.com>, Alistair Francis <alistair@alistair23.me>, "Edgar E. Iglesias" <edgar.iglesias@gmail.com>, Peter Maydell <peter.maydell@linaro.org>, "Cédric Le Goater" <clg@kaod.org>, Steven Lee <steven_lee@aspeedtech.com>, Troy Lee <leetroy@gmail.com>, Jamin Lin <jamin_lin@aspeedtech.com>, Andrew Jeffery <andrew@codeconstruct.com.au>, Joel Stanley <joel@jms.id.au>, Jason Wang <jasowang@redhat.com>, Sven Schnelle <svens@stackframe.org>, "Michael S. Tsirkin" <mst@redhat.com>, Rob Herring <robh@kernel.org>, Keith Busch <kbusch@kernel.org>, Klaus Jensen <its@irrelevant.dk>, Jesper Devantier <foss@defmacro.it>, Nicholas Piggin <npiggin@gmail.com>, "Frédéric Barrat" <fbarrat@linux.ibm.com>, Daniel Henrique Barboza <danielhb413@gmail.com>, Harsh Prateek Bora <harshpb@linux.ibm.com>, Fam Zheng <fam@euphon.net>, Hannes Reinecke <hare@suse.com>, Jeuk Kim <jeuk20.kim@samsung.com>

Expand all Fold all

[PATCH 30/31] net/socket: skip automatic zero-init of large array

Posted by Daniel P. Berrangé 5 months, 1 week ago

The 'net_socket_send' method has a 68k byte array used for copying
data between guest and host. Skip the automatic zero-init of this
array to eliminate the performance overhead in the I/O hot path.

The 'buf1' array will be fully initialized when reading data off
the network socket.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 net/socket.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/socket.c b/net/socket.c
index 8e3702e1f3..784dda686f 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -157,7 +157,7 @@ static void net_socket_send(void *opaque)
     NetSocketState *s = opaque;
     int size;
     int ret;
-    uint8_t buf1[NET_BUFSIZE];
+    QEMU_UNINITIALIZED uint8_t buf1[NET_BUFSIZE];
     const uint8_t *buf;
 
     size = recv(s->fd, buf1, sizeof(buf1), 0);
-- 
2.49.0