very high memory use

hi,
using 3.0.3.8, and a basic install, on Ubuntu 18.05, PHP 7.3, FCGI (CGI will not run, has to be FCGI)
only extra module is 'catalog mode'
running a image slideshow on the front page, 4 images, which themselves are not large, say 200KB each
Disabling the slideshow does not reduce the memory demand, hence a red herring
but memory use is HIGH, its killing my server which has 4GB
see below for mem use, all PHP 7.3, so many processes loaded by FCGI - not sure why so many are pre-loaded ? and how can they be reduced ?
see all these PID with memory use:

9426 illuminous 655.92 MiB /usr/bin/php-cgi7.3
9421 illuminous 655.27 MiB /usr/bin/php-cgi7.3
9407 illuminous 620.33 MiB /usr/bin/php-cgi7.3
9016 illuminous 605.76 MiB /usr/bin/php-cgi7.3
9012 illuminous 580.6 MiB /usr/bin/php-cgi7.3
8996 illuminous 580.46 MiB /usr/bin/php-cgi7.3
8999 illuminous 580.46 MiB /usr/bin/php-cgi7.3
9001 illuminous 580.46 MiB /usr/bin/php-cgi7.3
9004 illuminous 580.46 MiB /usr/bin/php-cgi7.3
9005 illuminous 580.46 MiB /usr/bin/php-cgi7.3
8997 illuminous 580.32 MiB /usr/bin/php-cgi7.3
8998 illuminous 580.32 MiB /usr/bin/php-cgi7.3
9000 illuminous 580.32 MiB /usr/bin/php-cgi7.3
9002 illuminous 580.32 MiB /usr/bin/php-cgi7.3
9006 illuminous 580.32 MiB /usr/bin/php-cgi7.3
9008 illuminous 580.32 MiB /usr/bin/php-cgi7.3
9009 illuminous 580.32 MiB /usr/bin/php-cgi7.3
9010 illuminous 580.32 MiB /usr/bin/php-cgi7.3
9011 illuminous 580.32 MiB /usr/bin/php-cgi7.3
9013 illuminous 580.32 MiB /usr/bin/php-cgi7.3
9014 illuminous 580.32 MiB /usr/bin/php-cgi7.3
9015 illuminous 580.32 MiB /usr/bin/php-cgi7.3
9017 illuminous 580.32 MiB /usr/bin/php-cgi7.3
9408 illuminous 580.32 MiB /usr/bin/php-cgi7.3
9409 illuminous 580.32 MiB /usr/bin/php-cgi7.3
9410 illuminous 580.32 MiB /usr/bin/php-cgi7.3
9411 illuminous 580.32 MiB /usr/bin/php-cgi7.3
9412 illuminous 580.32 MiB /usr/bin/php-cgi7.3
9413 illuminous 580.32 MiB /usr/bin/php-cgi7.3
9414 illuminous 580.32 MiB /usr/bin/php-cgi7.3
9415 illuminous 580.32 MiB /usr/bin/php-cgi7.3
9416 illuminous 580.32 MiB /usr/bin/php-cgi7.3
9417 illuminous 580.32 MiB /usr/bin/php-cgi7.3
9418 illuminous 580.32 MiB /usr/bin/php-cgi7.3
9419 illuminous 580.32 MiB /usr/bin/php-cgi7.3
9420 illuminous 580.32 MiB /usr/bin/php-cgi7.3
9422 illuminous 580.32 MiB /usr/bin/php-cgi7.3
9423 illuminous 580.32 MiB /usr/bin/php-cgi7.3
9424 illuminous 580.32 MiB /usr/bin/php-cgi7.3
9425 illuminous 580.32 MiB /usr/bin/php-cgi7.3

I wonder, could it be?
viewtopic.php?f=179&t=225771

TL;DR: Check your access logs and see if there's anything suspicious; if so, deny those connections before they can start a session.

it looks like a D.O.S attack

I installed the fix below, and it seems to have stopped the memory beyond 58% and zero virtual memory use  (vs 100/100)

https://www.opencart.com/index.php?rout ... n_id=43261