kvm/x86: multichase benchmark

[Yu Zhao]

On Thu, Jun 8, 2023 at 6:59 PM Yu Zhao <yuzhao at google.com> wrote:
>
> TLDR
> ====
> Multichase in 64 microVMs achieved 6% more total samples (in ~4 hours) after this patchset [1].
>
> Hardware
> ========
> HOST $ lscpu
> Architecture:            x86_64
>   CPU op-mode(s):        32-bit, 64-bit
>   Address sizes:         43 bits physical, 48 bits virtual
>   Byte Order:            Little Endian
> CPU(s):                  128
>   On-line CPU(s) list:   0-127
> Vendor ID:               AuthenticAMD
>   Model name:            AMD Ryzen Threadripper PRO 3995WX 64-Cores
>     CPU family:          23
>     Model:               49
>     Thread(s) per core:  2
>     Core(s) per socket:  64
>     Socket(s):           1
>     Stepping:            0
>     Frequency boost:     disabled
>     CPU max MHz:         4308.3979
>     CPU min MHz:         2200.0000
>     BogoMIPS:            5390.20
>     Flags:               fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2
>                          ...
> Virtualization features:
>   Virtualization:        AMD-V
> Caches (sum of all):
>   L1d:                   2 MiB (64 instances)
>   L1i:                   2 MiB (64 instances)
>   L2:                    32 MiB (64 instances)
>   L3:                    256 MiB (16 instances)
> NUMA:
>   NUMA node(s):          1
>   NUMA node0 CPU(s):     0-127
> Vulnerabilities:
>   Itlb multihit:         Not affected
>   L1tf:                  Not affected
>   Mds:                   Not affected
>   Meltdown:              Not affected
>   Mmio stale data:       Not affected
>   Retbleed:              Mitigation; untrained return thunk; SMT enabled with STIBP protection
>   Spec store bypass:     Mitigation; Speculative Store Bypass disabled via prctl
>   Spectre v1:            Mitigation; usercopy/swapgs barriers and __user pointer sanitization
>   Spectre v2:            Mitigation; Retpolines, IBPB conditional, STIBP always-on, RSB filling, PBRSB-eIBRS Not affected
>   Srbds:                 Not affected
>   Tsx async abort:       Not affected
>
> HOST $ numactl -H
> available: 1 nodes (0)
> node 0 cpus: 0-127
> node 0 size: 257542 MB
> node 0 free: 224855 MB
> node distances:
> node   0
>   0:  10
>
> HOST $ cat /sys/class/nvme/nvme0/model
> INTEL SSDPF21Q800GB
>
> HOST $ cat /sys/class/nvme/nvme0/numa_node
> 0
>
> Software
> ========
> HOST $ cat /etc/lsb-release
> DISTRIB_ID=Ubuntu
> DISTRIB_RELEASE=22.04
> DISTRIB_CODENAME=jammy
> DISTRIB_DESCRIPTION="Ubuntu 22.04.1 LTS"
>
> HOST $ uname -a
> Linux x86 6.4.0-rc5+ #1 SMP PREEMPT_DYNAMIC Wed Jun  7 22:17:47 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux
>
> HOST $ cat /proc/swaps
> Filename          Type         Size         Used    Priority
> /dev/nvme0n1p2    partition    466838356    0       -2
>
> HOST $ cat /sys/kernel/mm/lru_gen/enabled
> 0x000f
>
> HOST $ cat /sys/kernel/mm/transparent_hugepage/enabled
> always madvise [never]
>
> HOST $ cat /sys/kernel/mm/transparent_hugepage/defrag
> always defer defer+madvise madvise [never]
>
> Procedure
> =========
> HOST $ git clone https://github.com/google/multichase
>
> HOST $ <Build multichase>
> HOST $ <Unpack /boot/initrd.img into ./initrd/>
>
> HOST $ cp multichase/multichase ./initrd/bin/
> HOST $ sed -i \
>     "/^maybe_break top$/i multichase -t 2 -m 4g -n 28800; poweroff" \

I was reminded that I missed one parameter above, i.e.,

"/^maybe_break top$/i multichase -N -t 2 -m 4g -n 28800; poweroff" \
                                 ^^

>     ./initrd/init
>
> HOST $ <Pack ./initrd/ into ./initrd.img>
>
> HOST $ cat run_microvms.sh
> memcgs=64
>
> run() {
>     path=/sys/fs/cgroup/memcg$1
>
>     mkdir $path
>     echo $BASHPID >$path/cgroup.procs

And one line here:

echo 4000m >$path/memory.min # or the largest size that doesn't cause OOM kills

>     qemu-system-x86_64 -M microvm,accel=kvm -cpu host -smp 2 -m 6g \
>         -nographic -kernel /boot/vmlinuz -initrd ./initrd.img \
>         -append "console=ttyS0 loglevel=0"
> }
>
> for ((memcg = 0; memcg < $memcgs; memcg++)); do
>     run $memcg &
> done
>
> wait
>
> Results
> =======
>                  Before [1]    After    Change
> ----------------------------------------------
> Total samples    6824          7237     +6%
>
> Notes
> =====
> [1] "mm: rmap: Don't flush TLB after checking PTE young for page
>     reference" was included so that the comparison is apples to
>     Apples.
>     https://lore.kernel.org/r/20220706112041.3831-1-21cnbao@gmail.com/