From: "Daniel P. Berrangé" <berrange@redhat.com>
To: qemu-devel@nongnu.org
Cc: "Philippe Mathieu-Daudé" <philmd@linaro.org>,
"Michael S. Tsirkin" <mst@redhat.com>,
"Peter Maydell" <peter.maydell@linaro.org>,
qemu-block@nongnu.org, "Stefan Hajnoczi" <stefanha@redhat.com>,
"Kevin Wolf" <kwolf@redhat.com>,
"Daniel P. Berrangé" <berrange@redhat.com>
Subject: [PATCH 12/31] hw/audio/sb16: skip automatic zero-init of large array
Date: Tue, 10 Jun 2025 13:36:50 +0100 [thread overview]
Message-ID: <20250610123709.835102-13-berrange@redhat.com> (raw)
In-Reply-To: <20250610123709.835102-1-berrange@redhat.com>
The 'write_audio' method has a 4k byte array used for copying data
between the audio backend and device. Skip the automatic zero-init
of this array to eliminate the performance overhead in the I/O hot
path.
The 'tmpbuf' array will be fully initialized when reading data from
device memory.
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
hw/audio/sb16.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/hw/audio/sb16.c b/hw/audio/sb16.c
index 19fd3b9020..bac64118fe 100644
--- a/hw/audio/sb16.c
+++ b/hw/audio/sb16.c
@@ -1181,7 +1181,7 @@ static int write_audio (SB16State *s, int nchan, int dma_pos,
IsaDma *isa_dma = nchan == s->dma ? s->isa_dma : s->isa_hdma;
IsaDmaClass *k = ISADMA_GET_CLASS(isa_dma);
int temp, net;
- uint8_t tmpbuf[4096];
+ QEMU_UNINITIALIZED uint8_t tmpbuf[4096];
temp = len;
net = 0;
--
2.49.0
next prev parent reply other threads:[~2025-06-10 12:41 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-06-10 12:36 [PATCH 00/31] Skip automatic zero-init of large arrays / structs in I/O paths Daniel P. Berrangé
2025-06-10 12:36 ` [PATCH 01/31] include/qemu/compiler: add QEMU_UNINITIALIZED attribute macro Daniel P. Berrangé
2025-06-10 12:36 ` [PATCH 02/31] hw/virtio/virtio: avoid cost of -ftrivial-auto-var-init in hot path Daniel P. Berrangé
2025-06-10 12:36 ` [PATCH 03/31] block: skip automatic zero-init of large array in ioq_submit Daniel P. Berrangé
2025-06-10 12:36 ` [PATCH 04/31] chardev/char-fd: skip automatic zero-init of large array Daniel P. Berrangé
2025-06-10 12:36 ` [PATCH 05/31] chardev/char-pty: " Daniel P. Berrangé
2025-06-10 12:36 ` [PATCH 06/31] chardev/char-socket: " Daniel P. Berrangé
2025-06-10 12:36 ` [PATCH 07/31] hw/audio/ac97: skip automatic zero-init of large arrays Daniel P. Berrangé
2025-06-10 12:36 ` [PATCH 08/31] hw/audio/cs4231a: " Daniel P. Berrangé
2025-06-10 12:36 ` [PATCH 09/31] hw/audio/es1370: skip automatic zero-init of large array Daniel P. Berrangé
2025-06-10 12:36 ` [PATCH 10/31] hw/audio/gus: " Daniel P. Berrangé
2025-06-10 12:36 ` [PATCH 11/31] " Daniel P. Berrangé
2025-06-10 14:23 ` Daniel P. Berrangé
2025-06-10 12:36 ` Daniel P. Berrangé [this message]
2025-06-10 12:36 ` [PATCH 13/31] hw/audio/via-ac97: " Daniel P. Berrangé
2025-06-10 12:36 ` [PATCH 14/31] hw/char/sclpconsole-lm: " Daniel P. Berrangé
2025-06-10 12:36 ` [PATCH 15/31] hw/dma/xlnx_csu_dma: " Daniel P. Berrangé
2025-06-10 12:36 ` [PATCH 16/31] hw/display/vmware_vga: skip automatic zero-init of large struct Daniel P. Berrangé
2025-06-10 12:36 ` [PATCH 17/31] hw/hyperv/syndbg: skip automatic zero-init of large array Daniel P. Berrangé
2025-06-10 12:36 ` [PATCH 18/31] hw/misc/aspeed_hace: " Daniel P. Berrangé
2025-06-10 12:36 ` [PATCH 19/31] hw/net/rtl8139: " Daniel P. Berrangé
2025-06-10 12:36 ` [PATCH 20/31] hw/net/tulip: " Daniel P. Berrangé
2025-06-10 12:36 ` [PATCH 21/31] hw/net/virtio-net: skip automatic zero-init of large arrays Daniel P. Berrangé
2025-06-10 12:37 ` [PATCH 22/31] hw/net/xgamc: skip automatic zero-init of large array Daniel P. Berrangé
2025-06-10 12:37 ` [PATCH 23/31] hw/nvme/ctrl: skip automatic zero-init of large arrays Daniel P. Berrangé
2025-06-11 8:55 ` Klaus Jensen
2025-06-10 12:37 ` [PATCH 24/31] hw/ppc/pnv_occ: skip automatic zero-init of large struct Daniel P. Berrangé
2025-06-11 9:09 ` Harsh Prateek Bora
2025-06-10 12:37 ` [PATCH 25/31] hw/ppc/spapr_tpm_proxy: skip automatic zero-init of large arrays Daniel P. Berrangé
2025-06-11 9:20 ` Harsh Prateek Bora
2025-06-10 12:37 ` [PATCH 26/31] hw/usb/hcd-ohci: skip automatic zero-init of large array Daniel P. Berrangé
2025-06-10 12:37 ` [PATCH 27/31] hw/scsi/lsi53c895a: " Daniel P. Berrangé
2025-06-10 12:37 ` [PATCH 28/31] hw/scsi/megasas: skip automatic zero-init of large arrays Daniel P. Berrangé
2025-06-10 12:37 ` [PATCH 29/31] hw/ufs/lu: skip automatic zero-init of large array Daniel P. Berrangé
2025-06-10 12:37 ` [PATCH 30/31] net/socket: " Daniel P. Berrangé
2025-06-10 12:37 ` [PATCH 31/31] net/stream: " Daniel P. Berrangé
2025-06-10 12:49 ` [PATCH 00/31] Skip automatic zero-init of large arrays / structs in I/O paths Philippe Mathieu-Daudé
2025-06-10 12:56 ` Daniel P. Berrangé
2025-06-10 15:00 ` Philippe Mathieu-Daudé
2025-06-10 15:56 ` Daniel P. Berrangé
2025-06-10 14:04 ` Stefan Hajnoczi
2025-06-11 19:19 ` Stefan Hajnoczi
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