Re: [RFC PATCH 0/5] Memory access profiler(IBS) driven NUMA balancing

From: Huang, Ying
Date: Sun Feb 12 2023 - 22:27:37 EST

Bharata B Rao <bharata@xxxxxxx> writes:

> Hi,
>
> Some hardware platforms can provide information about memory accesses
> that can be used to do optimal page and task placement on NUMA
> systems. AMD processors have a hardware facility called Instruction-
> Based Sampling (IBS) that can be used to gather specific metrics
> related to instruction fetch and execution activity. This facility
> can be used to perform memory access profiling based on statistical
> sampling.
>
> This RFC is a proof-of-concept implementation where the access
> information obtained from the hardware is used to drive NUMA balancing.
> With this it is no longer necessary to scan the address space and
> introduce NUMA hint faults to build task-to-page association. Hence
> the approach taken here is to replace the address space scanning plus
> hint faults with the access information provided by the hardware.

You method can avoid the address space scanning, but cannot avoid memory
access fault in fact. PMU will raise NMI and then task_work to process
the sampled memory accesses. The overhead depends on the frequency of
the memory access sampling. Please measure the overhead of your method
in details.

> The access samples obtained from hardware are fed to NUMA balancing
> as fault-equivalents. The rest of the NUMA balancing logic that
> collects/aggregates the shared/private/local/remote faults and does
> pages/task migrations based on the faults is retained except that
> accesses replace faults.
>
> This early implementation is an attempt to get a working solution
> only and as such a lot of TODOs exist:
>
> - Perf uses IBS and we are using the same IBS for access profiling here.
> There needs to be a proper way to make the use mutually exclusive.
> - Is tying this up with NUMA balancing a reasonable approach or
> should we look at a completely new approach?
> - When accesses replace faults in NUMA balancing, a few things have
> to be tuned differently. All such decision points need to be
> identified and appropriate tuning needs to be done.
> - Hardware provided access information could be very useful for driving
> hot page promotion in tiered memory systems. Need to check if this
> requires different tuning/heuristics apart from what NUMA balancing
> already does.
> - Some of the values used to program the IBS counters like the sampling
> period etc may not be the optimal or ideal values. The sample period
> adjustment follows the same logic as scan period modification which
> may not be ideal. More experimentation is required to fine-tune all
> these aspects.
> - Currently I am acting (i,e., attempt to migrate a page) on each sampled
> access. Need to check if it makes sense to delay it and do batched page
> migration.

You current implementation is tied with AMD IBS. You will need a
architecture/vendor independent framework for upstreaming.

BTW: can IBS sampling memory writing too? Or just memory reading?

> This RFC is mainly about showing how hardware provided access
> information could be used for NUMA balancing but I have run a
> few basic benchmarks from mmtests to check if this is any severe
> regression/overhead to any of those. Some benchmarks show some
> improvement, some show no significant change and a few regress.
> I am hopeful that with more appropriate tuning there is scope for
> futher improvement here especially for workloads for which NUMA
> matters.

What's your expected improvement of the PMU based NUMA balancing? It
should come from reduced overhead? higher accuracy? Quicker response?
I think that it may be better to prove that with appropriate statistics
for at least one workload.

> FWIW, here are the numbers in brief:
> (1st column is default kernel, 2nd column is with this patchset)
>
> kernbench
> =========
> 6.2.0-rc5 6.2.0-rc5-ibs
> Amean user-512 19385.27 ( 0.00%) 18140.69 * 6.42%*
> Amean syst-512 21620.40 ( 0.00%) 19984.87 * 7.56%*
> Amean elsp-512 95.91 ( 0.00%) 88.60 * 7.62%*
>
> Duration User 19385.45 18140.89
> Duration System 21620.90 19985.37
> Duration Elapsed 96.52 89.20
>
> Ops NUMA alloc hit 552153976.00 499596610.00
> Ops NUMA alloc miss 0.00 0.00
> Ops NUMA interleave hit 0.00 0.00
> Ops NUMA alloc local 552152782.00 499595620.00
> Ops NUMA base-page range updates 758004.00 0.00
> Ops NUMA PTE updates 758004.00 0.00
> Ops NUMA PMD updates 0.00 0.00
> Ops NUMA hint faults 215654.00 1797848.00
> Ops NUMA hint local faults % 2054.00 1775103.00
> Ops NUMA hint local percent 0.95 98.73
> Ops NUMA pages migrated 213600.00 22745.00
> Ops AutoNUMA cost 1087.63 8989.67
>
> autonumabench
> =============
> Amean syst-NUMA01 90516.91 ( 0.00%) 65272.04 * 27.89%*
> Amean syst-NUMA01_THREADLOCAL 0.26 ( 0.00%) 0.27 * -3.80%*
> Amean syst-NUMA02 1.10 ( 0.00%) 1.02 * 7.24%*
> Amean syst-NUMA02_SMT 0.74 ( 0.00%) 0.90 * -21.77%*
> Amean elsp-NUMA01 747.73 ( 0.00%) 625.29 * 16.37%*
> Amean elsp-NUMA01_THREADLOCAL 1.07 ( 0.00%) 1.07 * -0.13%*
> Amean elsp-NUMA02 1.75 ( 0.00%) 1.72 * 1.96%*
> Amean elsp-NUMA02_SMT 3.03 ( 0.00%) 3.04 * -0.47%*
>
> Duration User 1312937.34 1148196.94
> Duration System 633634.59 456921.29
> Duration Elapsed 5289.47 4427.82
>
> Ops NUMA alloc hit 1115625106.00 704004226.00
> Ops NUMA alloc miss 0.00 0.00
> Ops NUMA interleave hit 0.00 0.00
> Ops NUMA alloc local 599879745.00 459968338.00
> Ops NUMA base-page range updates 74310268.00 0.00
> Ops NUMA PTE updates 74310268.00 0.00
> Ops NUMA PMD updates 0.00 0.00
> Ops NUMA hint faults 110504178.00 27624054.00
> Ops NUMA hint local faults % 54257985.00 17310888.00
> Ops NUMA hint local percent 49.10 62.67
> Ops NUMA pages migrated 11399016.00 7983717.00
> Ops AutoNUMA cost 553257.64 138271.96
>
> tbench4 Latency
> ===============
> Amean latency-1 0.08 ( 0.00%) 0.08 * 1.43%*
> Amean latency-2 0.10 ( 0.00%) 0.11 * -2.75%*
> Amean latency-4 0.14 ( 0.00%) 0.13 * 4.31%*
> Amean latency-8 0.14 ( 0.00%) 0.14 * -0.94%*
> Amean latency-16 0.20 ( 0.00%) 0.19 * 8.01%*
> Amean latency-32 0.24 ( 0.00%) 0.20 * 12.92%*
> Amean latency-64 0.34 ( 0.00%) 0.28 * 18.30%*
> Amean latency-128 1.71 ( 0.00%) 1.44 * 16.04%*
> Amean latency-256 0.52 ( 0.00%) 0.69 * -32.26%*
> Amean latency-512 3.27 ( 0.00%) 5.32 * -62.62%*
> Amean latency-1024 0.00 ( 0.00%) 0.00 * 0.00%*
> Amean latency-2048 0.00 ( 0.00%) 0.00 * 0.00%*
>
> tbench4 Throughput
> ==================
> Hmean 1 504.57 ( 0.00%) 496.80 * -1.54%*
> Hmean 2 1006.46 ( 0.00%) 990.04 * -1.63%*
> Hmean 4 1855.11 ( 0.00%) 1933.76 * 4.24%*
> Hmean 8 3711.49 ( 0.00%) 3582.32 * -3.48%*
> Hmean 16 6707.58 ( 0.00%) 6674.46 * -0.49%*
> Hmean 32 13146.81 ( 0.00%) 12649.49 * -3.78%*
> Hmean 64 20922.72 ( 0.00%) 22605.55 * 8.04%*
> Hmean 128 33637.07 ( 0.00%) 37870.35 * 12.59%*
> Hmean 256 54083.12 ( 0.00%) 50257.25 * -7.07%*
> Hmean 512 72455.66 ( 0.00%) 53141.88 * -26.66%*
> Hmean 1024 124413.95 ( 0.00%) 117398.40 * -5.64%*
> Hmean 2048 124481.61 ( 0.00%) 124892.12 * 0.33%*
>
> Ops NUMA alloc hit 2092196681.00 2007852353.00
> Ops NUMA alloc miss 0.00 0.00
> Ops NUMA interleave hit 0.00 0.00
> Ops NUMA alloc local 2092193601.00 2007849231.00
> Ops NUMA base-page range updates 298999.00 0.00
> Ops NUMA PTE updates 298999.00 0.00
> Ops NUMA PMD updates 0.00 0.00
> Ops NUMA hint faults 287539.00 4499166.00
> Ops NUMA hint local faults % 98931.00 4349685.00
> Ops NUMA hint local percent 34.41 96.68
> Ops NUMA pages migrated 169086.00 149476.00
> Ops AutoNUMA cost 1443.00 22498.67
>
> Duration User 23999.54 24476.30
> Duration System 160480.07 164366.91
> Duration Elapsed 2685.19 2685.69
>
> netperf-udp
> ===========
> Hmean send-64 226.57 ( 0.00%) 225.41 * -0.51%*
> Hmean send-128 450.89 ( 0.00%) 448.90 * -0.44%*
> Hmean send-256 899.63 ( 0.00%) 898.02 * -0.18%*
> Hmean send-1024 3510.63 ( 0.00%) 3526.24 * 0.44%*
> Hmean send-2048 6493.15 ( 0.00%) 6493.27 * 0.00%*
> Hmean send-3312 9778.22 ( 0.00%) 9801.03 * 0.23%*
> Hmean send-4096 11523.43 ( 0.00%) 11490.57 * -0.29%*
> Hmean send-8192 18666.11 ( 0.00%) 18686.99 * 0.11%*
> Hmean send-16384 28112.56 ( 0.00%) 28223.81 * 0.40%*
> Hmean recv-64 226.57 ( 0.00%) 225.41 * -0.51%*
> Hmean recv-128 450.88 ( 0.00%) 448.90 * -0.44%*
> Hmean recv-256 899.63 ( 0.00%) 898.01 * -0.18%*
> Hmean recv-1024 3510.61 ( 0.00%) 3526.21 * 0.44%*
> Hmean recv-2048 6493.07 ( 0.00%) 6493.15 * 0.00%*
> Hmean recv-3312 9777.95 ( 0.00%) 9800.85 * 0.23%*
> Hmean recv-4096 11522.87 ( 0.00%) 11490.47 * -0.28%*
> Hmean recv-8192 18665.83 ( 0.00%) 18686.56 * 0.11%*
> Hmean recv-16384 28112.13 ( 0.00%) 28223.73 * 0.40%*
>
> Duration User 48.52 48.74
> Duration System 931.24 925.83
> Duration Elapsed 1934.05 1934.79
>
> Ops NUMA alloc hit 60042365.00 60144256.00
> Ops NUMA alloc miss 0.00 0.00
> Ops NUMA interleave hit 0.00 0.00
> Ops NUMA alloc local 60042305.00 60144228.00
> Ops NUMA base-page range updates 6630.00 0.00
> Ops NUMA PTE updates 6630.00 0.00
> Ops NUMA PMD updates 0.00 0.00
> Ops NUMA hint faults 5709.00 26249.00
> Ops NUMA hint local faults % 3030.00 25130.00
> Ops NUMA hint local percent 53.07 95.74
> Ops NUMA pages migrated 2500.00 1119.00
> Ops AutoNUMA cost 28.64 131.27
>
> netperf-udp-rr
> ==============
> Hmean 1 132319.16 ( 0.00%) 130621.99 * -1.28%*
>
> Duration User 9.92 9.97
> Duration System 118.02 119.26
> Duration Elapsed 432.12 432.91
>
> Ops NUMA alloc hit 289650.00 289222.00
> Ops NUMA alloc miss 0.00 0.00
> Ops NUMA interleave hit 0.00 0.00
> Ops NUMA alloc local 289642.00 289222.00
> Ops NUMA base-page range updates 1.00 0.00
> Ops NUMA PTE updates 1.00 0.00
> Ops NUMA PMD updates 0.00 0.00
> Ops NUMA hint faults 1.00 51.00
> Ops NUMA hint local faults % 0.00 45.00
> Ops NUMA hint local percent 0.00 88.24
> Ops NUMA pages migrated 1.00 6.00
> Ops AutoNUMA cost 0.01 0.26
>
> netperf-tcp-rr
> ==============
> Hmean 1 118141.46 ( 0.00%) 115515.41 * -2.22%*
>
> Duration User 9.59 9.52
> Duration System 120.32 121.66
> Duration Elapsed 432.20 432.49
>
> Ops NUMA alloc hit 291257.00 290927.00
> Ops NUMA alloc miss 0.00 0.00
> Ops NUMA interleave hit 0.00 0.00
> Ops NUMA alloc local 291233.00 290923.00
> Ops NUMA base-page range updates 2.00 0.00
> Ops NUMA PTE updates 2.00 0.00
> Ops NUMA PMD updates 0.00 0.00
> Ops NUMA hint faults 2.00 46.00
> Ops NUMA hint local faults % 0.00 42.00
> Ops NUMA hint local percent 0.00 91.30
> Ops NUMA pages migrated 2.00 4.00
> Ops AutoNUMA cost 0.01 0.23
>
> dbench
> ======
> dbench4 Latency
>
> Amean latency-1 2.13 ( 0.00%) 10.92 *-411.44%*
> Amean latency-2 12.03 ( 0.00%) 8.17 * 32.07%*
> Amean latency-4 21.12 ( 0.00%) 9.60 * 54.55%*
> Amean latency-8 41.20 ( 0.00%) 33.59 * 18.45%*
> Amean latency-16 76.85 ( 0.00%) 75.84 * 1.31%*
> Amean latency-32 91.68 ( 0.00%) 90.26 * 1.55%*
> Amean latency-64 124.61 ( 0.00%) 113.31 * 9.07%*
> Amean latency-128 140.14 ( 0.00%) 126.29 * 9.89%*
> Amean latency-256 155.63 ( 0.00%) 142.11 * 8.69%*
> Amean latency-512 258.60 ( 0.00%) 243.13 * 5.98%*
>
> dbench4 Throughput (misleading but traditional)
>
> Hmean 1 987.47 ( 0.00%) 938.07 * -5.00%*
> Hmean 2 1750.10 ( 0.00%) 1697.08 * -3.03%*
> Hmean 4 2990.33 ( 0.00%) 3023.23 * 1.10%*
> Hmean 8 3557.38 ( 0.00%) 3863.32 * 8.60%*
> Hmean 16 2705.90 ( 0.00%) 2660.48 * -1.68%*
> Hmean 32 2954.08 ( 0.00%) 3101.59 * 4.99%*
> Hmean 64 3061.68 ( 0.00%) 3206.15 * 4.72%*
> Hmean 128 2867.74 ( 0.00%) 3080.21 * 7.41%*
> Hmean 256 2585.58 ( 0.00%) 2875.44 * 11.21%*
> Hmean 512 1777.80 ( 0.00%) 1777.79 * -0.00%*
>
> Duration User 2359.02 2246.44
> Duration System 18927.83 16856.91
> Duration Elapsed 1901.54 1901.44
>
> Ops NUMA alloc hit 240556255.00 255283721.00
> Ops NUMA alloc miss 408851.00 62903.00
> Ops NUMA interleave hit 0.00 0.00
> Ops NUMA alloc local 240547816.00 255264974.00
> Ops NUMA base-page range updates 204316.00 0.00
> Ops NUMA PTE updates 204316.00 0.00
> Ops NUMA PMD updates 0.00 0.00
> Ops NUMA hint faults 201101.00 287642.00
> Ops NUMA hint local faults % 104199.00 153547.00
> Ops NUMA hint local percent 51.81 53.38
> Ops NUMA pages migrated 96158.00 134083.00
> Ops AutoNUMA cost 1008.76 1440.76
>
> Bharata B Rao (5):
> x86/ibs: In-kernel IBS driver for page access profiling
> x86/ibs: Drive NUMA balancing via IBS access data
> x86/ibs: Enable per-process IBS from sched switch path
> x86/ibs: Adjust access faults sampling period
> x86/ibs: Delay the collection of HW-provided access info
>
> arch/x86/events/amd/ibs.c | 6 +
> arch/x86/include/asm/msr-index.h | 12 ++
> arch/x86/mm/Makefile | 1 +
> arch/x86/mm/ibs.c | 250 +++++++++++++++++++++++++++++++
> include/linux/migrate.h | 1 +
> include/linux/mm.h | 2 +
> include/linux/mm_types.h | 3 +
> include/linux/sched.h | 4 +
> include/linux/vm_event_item.h | 12 ++
> kernel/sched/core.c | 1 +
> kernel/sched/debug.c | 10 ++
> kernel/sched/fair.c | 142 ++++++++++++++++--
> kernel/sched/sched.h | 9 ++
> mm/memory.c | 92 ++++++++++++
> mm/vmstat.c | 12 ++
> 15 files changed, 544 insertions(+), 13 deletions(-)
> create mode 100644 arch/x86/mm/ibs.c

Best Regards,
Huang, Ying