48 lines
1.8 KiB
Diff
48 lines
1.8 KiB
Diff
From f9a1a355dbd2d59bbd80d33e713579d93fe3932f Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= <berrange@redhat.com>
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Date: Tue, 10 Jun 2025 13:36:58 +0100
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Subject: [PATCH 21/31] hw/net/tulip: skip automatic zero-init of large array
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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RH-Author: Stefan Hajnoczi <stefanha@redhat.com>
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RH-MergeRequest: 461: Solve -ftrivial-auto-var-init performance regression with QEMU_UNINITIALIZED
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RH-Jira: RHEL-99887
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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RH-Commit: [20/30] ff60b673f4e06a25fd5efbc51f5536da5d9c99f5
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The 'tulip_setup_frame' method has a 4k byte array used for copynig
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DMA data from the device. Skip the automatic zero-init of this array
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to eliminate the performance overhead in the I/O hot path.
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The 'buf' array will be fully initialized when reading data from the
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device.
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Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
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Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
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Message-id: 20250610123709.835102-21-berrange@redhat.com
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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(cherry picked from commit e1afd5ee6eb2954f4baf3c97820e4aaf7de97d2a)
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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---
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hw/net/tulip.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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diff --git a/hw/net/tulip.c b/hw/net/tulip.c
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index 1f2ef20977..5cf2b96fbd 100644
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--- a/hw/net/tulip.c
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+++ b/hw/net/tulip.c
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@@ -629,7 +629,7 @@ static void tulip_setup_filter_addr(TULIPState *s, uint8_t *buf, int n)
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static void tulip_setup_frame(TULIPState *s,
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struct tulip_descriptor *desc)
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{
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- uint8_t buf[4096];
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+ QEMU_UNINITIALIZED uint8_t buf[4096];
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int len = (desc->control >> TDES1_BUF1_SIZE_SHIFT) & TDES1_BUF1_SIZE_MASK;
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int i;
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--
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2.39.3
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