Memory builds up when creating size-zero NDArray in a loop

[yuxihu]

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Description

Memory builds up when creating size-zero ndarray in a loop

Environment info (Required)

----------Python Info----------
('Version      :', '2.7.15')
('Compiler     :', 'GCC 7.2.0')
('Build        :', ('default', 'May  1 2018 23:32:55'))
('Arch         :', ('64bit', ''))
------------Pip Info-----------
('Version      :', '10.0.1')
('Directory    :', '/home/ubuntu/anaconda3/envs/python2/lib/python2.7/site-packages/pip')
----------MXNet Info-----------
('Version      :', '1.4.0')
('Directory    :', '/home/ubuntu/anaconda3/envs/python2/lib/python2.7/site-packages/mxnet')
('Commit Hash   :', 'a03d59ed867ba334d78d61246a1090cd1868f5da')
----------System Info----------
('Platform     :', 'Linux-4.4.0-1075-aws-x86_64-with-debian-stretch-sid')
('system       :', 'Linux')
('node         :', 'ip-172-31-4-52')
('release      :', '4.4.0-1075-aws')
('version      :', '#85-Ubuntu SMP Thu Jan 17 17:15:12 UTC 2019')
----------Hardware Info----------
('machine      :', 'x86_64')
('processor    :', 'x86_64')
Architecture:          x86_64
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Little Endian
CPU(s):                32
On-line CPU(s) list:   0-31
Thread(s) per core:    2
Core(s) per socket:    16
Socket(s):             1
NUMA node(s):          1
Vendor ID:             GenuineIntel
CPU family:            6
Model:                 79
Model name:            Intel(R) Xeon(R) CPU E5-2686 v4 @ 2.30GHz
Stepping:              1
CPU MHz:               2699.984
CPU max MHz:           3000.0000
CPU min MHz:           1200.0000
BogoMIPS:              4600.09
Hypervisor vendor:     Xen
Virtualization type:   full
L1d cache:             32K
L1i cache:             32K
L2 cache:              256K
L3 cache:              46080K
NUMA node0 CPU(s):     0-31
Flags:                 fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx pdpe1gb rdtscp lm constant_tsc rep_good nopl xtopology nonstop_tsc aperfmperf pni pclmulqdq ssse3 fma cx16 pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand hypervisor lahf_lm abm 3dnowprefetch invpcid_single kaiser fsgsbase bmi1 hle avx2 smep bmi2 erms invpcid rtm rdseed adx xsaveopt
----------Network Test----------
Setting timeout: 10
Timing for MXNet: https://github.com/apache/incubator-mxnet, DNS: 0.0021 sec, LOAD: 0.6245 sec.
Timing for PYPI: https://pypi.python.org/pypi/pip, DNS: 0.0071 sec, LOAD: 0.3581 sec.
Timing for FashionMNIST: https://apache-mxnet.s3-accelerate.dualstack.amazonaws.com/gluon/dataset/fashion-mnist/train-labels-idx1-ubyte.gz, DNS: 0.0265 sec, LOAD: 0.0987 sec.
Timing for Conda: https://repo.continuum.io/pkgs/free/, DNS: 0.0080 sec, LOAD: 0.0543 sec.
Timing for Gluon Tutorial(en): http://gluon.mxnet.io, DNS: 0.1285 sec, LOAD: 0.1622 sec.
Timing for Gluon Tutorial(cn): https://zh.gluon.ai, DNS: 0.3537 sec, LOAD: 0.3427 sec.

Package used (Python/R/Scala/Julia): Python

Error Message:

If you run watch -n5 nvidia-smi, you may observe memory growth every by 2MB every few seconds.

Minimum reproducible example

import mxnet as mx
import time

count = 0
while True:
    a = mx.nd.array([], ctx=mx.gpu(0))
    a.asnumpy()
    time.sleep(0.01)
    count += 1
    if count % 1000 == 0:
        print(count)

Steps to reproduce

(Paste the commands you ran that produced the error.)

1. Put the above code into a file called leak.py
2. python leak.py
3. watch -n5 nvidia-smi

What have you tried to solve it?

1. Create non size-zero ndarray (e.g. mx.nd.array([1], ctx=mx.gpu(1))) in the loop and there is no memory builds-up issue. But the issue remains with size-zero ndarray

Related to #13951

[mxnet-label-bot]

Hey, this is the MXNet Label Bot.
Thank you for submitting the issue! I will try and suggest some labels so that the appropriate MXNet community members can help resolve it.
Here are my recommended labels: Bug

[yuxihu]

@mxnet-label-bot update [Bug, NDArray, CUDA]

[yuxihu]

We still observe the same issue after changing context from mx.gpu(0) to mx.cpu(0).

@mxnet-label-bot update [Bug, NDArray]

[yuxihu]

@mxnet-label-bot add [Backend, Memory]

[anirudh2290]

Nice catch !

[yuxihu]

@anirudh2290 Could you please reopen this? The original fix has been reverted due to test flakiness. I am working on alternative fix.