On Mon, Jan 30, 2023 at 10:32:56AM +0800, kernel test robot wrote:
> FYI, we noticed a -19.2% regression of unixbench.score due to commit:
>
> commit: f1a7941243c102a44e8847e3b94ff4ff3ec56f25 ("mm: convert mm's rss stats into percpu_counter")
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
>
> in testcase: unixbench
> on test machine: 128 threads 4 sockets Intel(R) Xeon(R) Gold 6338 CPU @ 2.00GHz (Ice Lake) with 256G memory
> with following parameters:
>
> runtime: 300s
> nr_task: 30%
> test: spawn
> cpufreq_governor: performance
...
> 9cd6ffa60256e931 f1a7941243c102a44e8847e3b94
> ---------------- ---------------------------
> %stddev %change %stddev
> \ | \
> 11110 -19.2% 8974 unixbench.score
> 1090843 -12.2% 957314 unixbench.time.involuntary_context_switches
> 4243909 ± 6% -32.4% 2867136 ± 5% unixbench.time.major_page_faults
> 10547 -12.6% 9216 unixbench.time.maximum_resident_set_size
> 9.913e+08 -19.6% 7.969e+08 unixbench.time.minor_page_faults
> 5638 +19.1% 6714 unixbench.time.system_time
> 5502 -20.7% 4363 unixbench.time.user_time
So we're spending a lot more time in the kernel and correspondingly less
time in userspace.
> 67991885 -16.9% 56507507 unixbench.time.voluntary_context_switches
> 46198768 -19.1% 37355723 unixbench.workload
> 1.365e+08 -12.5% 1.195e+08 ± 7% cpuidle..usage
> 1220612 ± 4% -38.0% 757009 ± 28% meminfo.Active
> 1220354 ± 4% -38.0% 756754 ± 28% meminfo.Active(anon)
> 0.50 ± 2% -0.1 0.45 ± 4% mpstat.cpu.all.soft%
> 1.73 -0.2 1.52 ± 2% mpstat.cpu.all.usr%
> 532266 -18.4% 434559 vmstat.system.cs
> 495826 -12.2% 435455 ± 8% vmstat.system.in
> 1.36e+08 -13.2% 1.18e+08 ± 9% turbostat.C1
> 68.80 +0.8 69.60 turbostat.C1%
> 1.663e+08 -12.1% 1.462e+08 ± 8% turbostat.IRQ
> 15.54 ± 20% -49.0% 7.93 ± 24% sched_debug.cfs_rq:/.runnable_avg.min
> 13.26 ± 19% -46.6% 7.08 ± 29% sched_debug.cfs_rq:/.util_avg.min
> 48.96 ± 8% +51.5% 74.20 ± 13% sched_debug.cfs_rq:/.util_est_enqueued.avg
> 138.00 ± 5% +28.9% 177.87 ± 7% sched_debug.cfs_rq:/.util_est_enqueued.stddev
> 228060 ± 3% +13.3% 258413 ± 4% sched_debug.cpu.avg_idle.stddev
> 432533 ± 5% -16.4% 361517 ± 4% sched_debug.cpu.nr_switches.min
> 2.665e+08 -18.9% 2.162e+08 numa-numastat.node0.local_node
> 2.666e+08 -18.9% 2.163e+08 numa-numastat.node0.numa_hit
> 2.746e+08 -20.9% 2.172e+08 numa-numastat.node1.local_node
> 2.747e+08 -20.9% 2.172e+08 numa-numastat.node1.numa_hit
> 2.602e+08 -17.4% 2.149e+08 numa-numastat.node2.local_node
> 2.603e+08 -17.4% 2.149e+08 numa-numastat.node2.numa_hit
> 2.423e+08 -15.0% 2.06e+08 numa-numastat.node3.local_node
> 2.424e+08 -15.0% 2.061e+08 numa-numastat.node3.numa_hit
So we're going off-node a lot more for ... something.
> 2.666e+08 -18.9% 2.163e+08 numa-vmstat.node0.numa_hit
> 2.665e+08 -18.9% 2.162e+08 numa-vmstat.node0.numa_local
> 2.747e+08 -20.9% 2.172e+08 numa-vmstat.node1.numa_hit
> 2.746e+08 -20.9% 2.172e+08 numa-vmstat.node1.numa_local
> 2.603e+08 -17.4% 2.149e+08 numa-vmstat.node2.numa_hit
> 2.602e+08 -17.4% 2.149e+08 numa-vmstat.node2.numa_local
> 2.424e+08 -15.0% 2.061e+08 numa-vmstat.node3.numa_hit
> 2.423e+08 -15.0% 2.06e+08 numa-vmstat.node3.numa_local
> 304947 ± 4% -38.0% 189144 ± 28% proc-vmstat.nr_active_anon
Umm. Are we running vmstat a lot during this test? The commit says:
At the
moment the readers are either procfs interface, oom_killer and memory
reclaim which I think are not performance critical and should be ok with
slow read. However I think we can make that change in a separate patch.
This would explain the increased cross-NUMA references (we're going to
the other nodes to collect the stats), and the general slowdown. But I
don't think it reflects a real workload; it's reflecting that the
monitoring of this workload that we're doing is now more accurate and
more expensive.
