50 lines
1.8 KiB
Diff
50 lines
1.8 KiB
Diff
From c336909ad95540147d9cfed843874ddd986ad917 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 13:36:42 +0100
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Subject: [PATCH 05/31] chardev/char-fd: skip automatic zero-init of large
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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: [4/30] e9adf42d47ddd90cc15862e711de0a90d1d25e0a
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The 'fd_chr_read' method has a 4k byte array used for copying
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data between the socket and device. Skip the automatic zero-init
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of this array to eliminate the performance overhead in the I/O
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hot path.
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The 'buf' array will be fully initialized when reading data off
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the network socket.
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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: 20250610123709.835102-5-berrange@redhat.com
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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(cherry picked from commit a503bdc22b91869e3bf45522e36b122889465306)
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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---
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chardev/char-fd.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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diff --git a/chardev/char-fd.c b/chardev/char-fd.c
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index d2c4923359..8dd662c066 100644
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--- a/chardev/char-fd.c
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+++ b/chardev/char-fd.c
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@@ -50,7 +50,7 @@ static gboolean fd_chr_read(QIOChannel *chan, GIOCondition cond, void *opaque)
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Chardev *chr = CHARDEV(opaque);
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FDChardev *s = FD_CHARDEV(opaque);
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int len;
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- uint8_t buf[CHR_READ_BUF_LEN];
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+ QEMU_UNINITIALIZED uint8_t buf[CHR_READ_BUF_LEN];
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ssize_t ret;
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len = sizeof(buf);
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--
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2.39.3
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