Re: [PATCH v2] IPI performance benchmark
From: Yury Norov
Date: Thu Dec 21 2017 - 14:03:23 EST
On Wed, Dec 20, 2017 at 02:44:25PM +0800, Wanpeng Li wrote:
> Hi Yury,
> 2017-12-19 16:50 GMT+08:00 Yury Norov <ynorov@xxxxxxxxxxxxxxxxxx>:
> > This benchmark sends many IPIs in different modes and measures
> > time for IPI delivery (first column), and total time, ie including
> > time to acknowledge the receive by sender (second column).
> > The scenarios are:
> > Dry-run: do everything except actually sending IPI. Useful
> > to estimate system overhead.
> > Self-IPI: Send IPI to self CPU.
> > Normal IPI: Send IPI to some other CPU.
> > Broadcast IPI: Send broadcast IPI to all online CPUs.
> > Broadcast lock: Send broadcast IPI to all online CPUs and force them
> > acquire/release spinlock.
> > The raw output looks like this:
> > [ 155.363374] Dry-run: 0, 2999696 ns
> > [ 155.429162] Self-IPI: 30385328, 65589392 ns
> > [ 156.060821] Normal IPI: 566914128, 631453008 ns
> > [ 158.384427] Broadcast IPI: 0, 2323368720 ns
> > [ 160.831850] Broadcast lock: 0, 2447000544 ns
> > For virtualized guests, sending and reveiving IPIs causes guest exit.
> > I used this test to measure performance impact on KVM subsystem of
> > Christoffer Dall's series "Optimize KVM/ARM for VHE systems" .
> > Test machine is ThunderX2, 112 online CPUs. Below the results normalized
> > to host dry-run time, broadcast lock results omitted. Smaller - better.
> Could you test on a x86 box? I see a lot of calltraces on my haswell
> client host, there is no calltrace in the guest, however, I can still
> observe "Invalid parameters" warning when insmod this module. In
> addition, the x86 box fails to boot when ipi_benchmark is buildin.
I tried to boot kernel with builtin test both on real hardware and
qemu+kvm - no calltraces or other problems. Kernel is 4.14, config for
host is attached.
CPU is Intel(R) Core(TM) i7-7600U CPU @ 2.80GHz
Kernel is 4.14, config for host is attached, but it's default Ubuntu
config. Results and qemu command are below. Could you share more details
about your configuration?
qemu-system-x86_64 -hda debian_squeeze_amd64_standard.qcow2 \
-smp 1 -curses --nographic --enable-kvm
Host, 4 cores:
[ 0.237279] Dry-run: 0, 170292 ns
[ 0.643269] Self-IPI: 458516336, 922256372 ns
[ 0.902545] Self-IPI: 508518362, 972130665 ns
[ 0.646500] Broadcast IPI: 0, 97301545 ns
[ 0.649712] Broadcast lock: 0, 102364755 ns
KVM, single core:
[ 0.237279] Dry-run: 0, 124500 ns
[ 0.643269] Self-IPI: 202518310, 405444790 ns
[ 0.643694] Normal IPI FAILED: -2
[ 0.646500] Broadcast IPI: 0, 2524370 ns
[ 0.649712] Broadcast lock: 0, 2642270 ns
KVM, 4 cores:
[ 0.492676] Dry-run: 0, 126380 ns
[ 0.902545] Self-IPI: 204085450, 409863800 ns
[ 2.179676] Normal IPI: 1058014940, 1276742820 ns
[ 3.396132] Broadcast IPI: 0, 1215934730 ns
[ 4.610719] Broadcast lock: 0, 1213945500 ns