High memory usage by Xorg with Kubuntu 18.04, plasma-desktop, nvidia 390

[Optimus Prime]

After some continued use of the system (Kubuntu (18.04)) Xorg accumulates a lot of RAM space. From that the space only increments and doesn't decrease.

Hardware Specs :

1. Intel core-i5 6300 HQ
2. Nvidia GTX 960M

Software Specs :

1. Kubuntu 18.04
2. KDE Plasma shell version 5.12.7

Something interesting to note is that I have not experienced the same behavior from Xorg when I switch the GPU to Intel's Integrated graphics. It is entirely possible that I might not have been able to trigger those situation with Intel, because after seeing logs I couldn't make out why this was happening.

Also for the timeline I have used the system for over an year without any such issue arising. It was the second week of June 2019 to present day I have seen this problem.

Xorg log : http://paste.ubuntu.com/p/nc3pMF4xsb/

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: xorg 1:7.7+19ubuntu7.1
ProcVersionSignature: Ubuntu 4.18.0-22.23~18.04.1-generic 4.18.20
Uname: Linux 4.18.0-22-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
.proc.driver.nvidia.gpus.0000.02.00.0: Error: [Errno 21] Is a directory: '/proc/driver/nvidia/gpus/0000:02:00.0'
.proc.driver.nvidia.registry: Binary: ""
.proc.driver.nvidia.version:
 NVRM version: NVIDIA UNIX x86_64 Kernel Module 390.116 Sun Jan 27 07:21:36 PST 2019
 GCC version: gcc version 7.4.0 (Ubuntu 7.4.0-1ubuntu1~18.04.1)
ApportVersion: 2.20.9-0ubuntu7.6
Architecture: amd64
BootLog: Error: [Errno 13] Permission denied: '/var/log/boot.log'
CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins'
CompositorRunning: None
CurrentDesktop: KDE
Date: Sun Jun 23 05:06:48 2019
DistUpgraded: Fresh install
DistroCodename: bionic
DistroVariant: ubuntu
DkmsStatus: nvidia, 390.116, 4.18.0-22-generic, x86_64: installed
ExtraDebuggingInterest: Yes, if not too technical
GraphicsCard:
 Intel Corporation HD Graphics 530 [8086:191b] (rev 06) (prog-if 00 [VGA controller])
   Subsystem: Dell HD Graphics 530 [1028:0706]
   Subsystem: Dell GM107M [GeForce GTX 960M] [1028:0706]
InstallationDate: Installed on 2019-06-21 (1 days ago)
InstallationMedia: Kubuntu 18.04.2 LTS "Bionic Beaver" - Release amd64 (20190210)
Lsusb:
 Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
 Bus 001 Device 004: ID 8087:0a2a Intel Corp.
 Bus 001 Device 003: ID 1bcf:28b0 Sunplus Innovation Technology Inc.
 Bus 001 Device 002: ID 413c:301a Dell Computer Corp.
 Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
MachineType: Dell Inc. Inspiron 7559
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.18.0-22-generic root=UUID=f046965f-7377-42b2-86ba-febdbcabfc9b ro quiet splash vt.handoff=1
SourcePackage: xorg
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 12/13/2017
dmi.bios.vendor: Dell Inc.
dmi.bios.version: 1.2.7
dmi.board.name: 0H87XC
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.type: 10
dmi.chassis.vendor: Dell Inc.
dmi.chassis.version: Not Specified
dmi.modalias: dmi:bvnDellInc.:bvr1.2.7:bd12/13/2017:svnDellInc.:pnInspiron7559:pvr1.2.7:rvnDellInc.:rn0H87XC:rvrA00:cvnDellInc.:ct10:cvrNotSpecified:
dmi.product.family: Inspiron
dmi.product.name: Inspiron 7559
dmi.product.sku: 0706
dmi.product.version: 1.2.7
dmi.sys.vendor: Dell Inc.
version.compiz: compiz N/A
version.libdrm2: libdrm2 2.4.95-1~18.04.1
version.libgl1-mesa-dri: libgl1-mesa-dri 18.2.8-0ubuntu0~18.04.2
version.libgl1-mesa-glx: libgl1-mesa-glx 18.2.8-0ubuntu0~18.04.2
version.nvidia-graphics-drivers: nvidia-graphics-drivers-* N/A
version.xserver-xorg-core: xserver-xorg-core N/A
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev N/A
version.xserver-xorg-video-ati: xserver-xorg-video-ati N/A
version.xserver-xorg-video-intel: xserver-xorg-video-intel N/A
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau N/A