From 7c889953afbf830cb4522ec259221a9319c0f42a Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= Date: Tue, 10 Jun 2025 13:36:48 +0100 Subject: [PATCH 18/43] hw/audio/gus: skip automatic zero-init of large array MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit RH-Author: Stefan Hajnoczi RH-MergeRequest: 381: Solve -ftrivial-auto-var-init performance regression with QEMU_UNINITIALIZED RH-Jira: RHEL-95479 RH-Acked-by: Miroslav Rezanina RH-Commit: [10/31] a580b7fae56231c7bf1e2b797a4037eeb45f817a (stefanha/centos-stream-qemu-kvm) The 'GUS_read_DMA' 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 Reviewed-by: Stefan Hajnoczi Message-id: 20250610123709.835102-11-berrange@redhat.com Signed-off-by: Stefan Hajnoczi (cherry picked from commit 2e438da4929018c62609381e1156aac0b2fe3de3) Signed-off-by: Stefan Hajnoczi --- hw/audio/gus.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/hw/audio/gus.c b/hw/audio/gus.c index e718c1183e..bd242e19a3 100644 --- a/hw/audio/gus.c +++ b/hw/audio/gus.c @@ -183,7 +183,7 @@ static int GUS_read_DMA (void *opaque, int nchan, int dma_pos, int dma_len) { GUSState *s = opaque; IsaDmaClass *k = ISADMA_GET_CLASS(s->isa_dma); - char tmpbuf[4096]; + QEMU_UNINITIALIZED char tmpbuf[4096]; int pos = dma_pos, mode, left = dma_len - dma_pos; ldebug ("read DMA %#x %d\n", dma_pos, dma_len); -- 2.39.3