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While this loses quite a bit of accuracy (although to no apparent decrease in emulation quality) , it helps avoiding the additional overhead of the `clock_gettime` syscall (as `CLOCK_MONOTONIC_COARSE` is forwarded using the mapped time page) and we don't have to do a HPET timer read for each tick. This results in a decrease of Serenity boot time from 1h16m down to 42m when running on Serenity.
28 lines
1.1 KiB
Diff
28 lines
1.1 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Tim Schumacher <timschumi@gmx.de>
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Date: Sat, 1 Oct 2022 02:46:48 +0200
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Subject: [PATCH] Use the coarse monotonic clock for timing CPU ticks
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While this loses quite a bit of accuracy (although to no apparent
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decrease in emulation quality), it helps avoiding the additional
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overhead of the `clock_gettime` syscall (as `CLOCK_MONOTONIC_COARSE`
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is forwarded using the mapped time page) and we don't have to do a
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HPET timer read for each tick.
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---
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include/qemu/timer.h | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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diff --git a/include/qemu/timer.h b/include/qemu/timer.h
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index ee071e07d131641131ed9705e7407f153bbf6c67..97fb9b9ac28bd36cd7200e92c3c0c1e30858aa0d 100644
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--- a/include/qemu/timer.h
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+++ b/include/qemu/timer.h
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@@ -833,7 +833,7 @@ static inline int64_t get_clock(void)
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{
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if (use_rt_clock) {
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struct timespec ts;
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- clock_gettime(CLOCK_MONOTONIC, &ts);
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+ clock_gettime(CLOCK_MONOTONIC_COARSE, &ts);
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return ts.tv_sec * 1000000000LL + ts.tv_nsec;
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} else {
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/* XXX: using gettimeofday leads to problems if the date
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