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[Qemu-devel] [Bug 1774677] Re: -icount increases boot time by >10x
From: |
Pavel Dovgalyuk |
Subject: |
[Qemu-devel] [Bug 1774677] Re: -icount increases boot time by >10x |
Date: |
Mon, 09 Jul 2018 11:54:30 -0000 |
Yes, I tried to revert (with some updates to the current code base) and
the bug was fixed:
diff --git a/cpus.c b/cpus.c
index 181ce33..e2fc972 100644
--- a/cpus.c
+++ b/cpus.c
@@ -1172,6 +1172,13 @@ static void qemu_tcg_rr_wait_io_event(CPUState *cpu)
{
while (all_cpu_threads_idle()) {
stop_tcg_kick_timer();
+
+ qemu_mutex_unlock_iothread();
+ replay_mutex_lock();
+ qemu_mutex_lock_iothread();
+ qemu_start_warp_timer();
+ replay_mutex_unlock();
+
qemu_cond_wait(cpu->halt_cond, &qemu_global_mutex);
}
--
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https://bugs.launchpad.net/bugs/1774677
Title:
-icount increases boot time by >10x
Status in QEMU:
Confirmed
Bug description:
When I specify the -icount option, some guest operations such as
booting a Linux kernel take more than 10 times longer than otherwise.
For example, the following will boot Aboriginal Linux to the login
prompt about 6 seconds on my system (using TCG, not KVM):
wget
http://landley.net/aboriginal/downloads/old/binaries/1.4.5/system-image-i686.tar.gz
gunzip <system-image-i686.tar.gz | tar xfv -
cd system-image-i686
sh run-emulator.sh
If I replace the last line with
QEMU_EXTRA="-icount shift=auto" sh run-emulator.sh
booting to the login prompt takes about 1 minute 20 seconds.
I have tried different values for "shift" other than the "auto" used
above, but have not been able to find one that gives reasonable
performance. Specifying "sleep=off" also did not help.
During the slow boots, qemu appears to spend most of its time
sleeping, not using the host CPU.
I see this with multiple versions of qemu, including current git
sources (c181ddaa176856b3cd2dfd12bbcf25fa9c884a97), and on multiple
host OSes, including Debian 9 on x86_64.
To manage notifications about this bug go to:
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- [Qemu-devel] [Bug 1774677] Re: -icount increases boot time by >10x, Peter Maydell, 2018/07/06
- [Qemu-devel] [Bug 1774677] Re: -icount increases boot time by >10x, Peter Maydell, 2018/07/06
- [Qemu-devel] [Bug 1774677] Re: -icount increases boot time by >10x, Peter Maydell, 2018/07/06
- [Qemu-devel] [Bug 1774677] Re: -icount increases boot time by >10x, Andreas Gustafsson, 2018/07/06
- [Qemu-devel] [Bug 1774677] Re: -icount increases boot time by >10x, Andreas Gustafsson, 2018/07/08
- [Qemu-devel] [Bug 1774677] Re: -icount increases boot time by >10x, Pavel Dovgalyuk, 2018/07/09
- [Qemu-devel] [Bug 1774677] Re: -icount increases boot time by >10x, Paolo Bonzini, 2018/07/09
- [Qemu-devel] [Bug 1774677] Re: -icount increases boot time by >10x,
Pavel Dovgalyuk <=
- [Qemu-devel] [Bug 1774677] Re: -icount increases boot time by >10x, Andreas Gustafsson, 2018/07/12
- [Qemu-devel] [Bug 1774677] Re: -icount increases boot time by >10x, Pavel Dovgalyuk, 2018/07/12