50 lines
1.8 KiB
Diff
50 lines
1.8 KiB
Diff
From 489ead1e7d721c0f689626e6d5d22241ffdd7bc8 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 13:36:43 +0100
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Subject: [PATCH 06/31] chardev/char-pty: 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: [5/30] 09be65fa8c25dadbd472321cacc96badf0a2d963
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The 'pty_chr_read' method has a 4k byte array used for copying
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data between the PTY 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 PTY.
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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: 20250610123709.835102-6-berrange@redhat.com
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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(cherry picked from commit 45bb7fb21c8d18294a9f92da99d01ab3c67c7df2)
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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---
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chardev/char-pty.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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diff --git a/chardev/char-pty.c b/chardev/char-pty.c
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index cc2f7617fe..3319ad215d 100644
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--- a/chardev/char-pty.c
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+++ b/chardev/char-pty.c
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@@ -152,7 +152,7 @@ static gboolean pty_chr_read(QIOChannel *chan, GIOCondition cond, void *opaque)
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Chardev *chr = CHARDEV(opaque);
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PtyChardev *s = PTY_CHARDEV(opaque);
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gsize 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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