Re: [PATCH v2] IPI performance benchmark

From: Wanpeng Li
Date: Wed Dec 20 2017 - 01:44:35 EST

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" [1].
> 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.

Wanpeng Li