I might have worked something out, are CloudLinux virtual memory limits compatible with Litespeed LSAPI + deamon mode ?
I had limits of 2GB per account and before PHP crashed I think PHP's processes were using up 2GB (currently using 1.3GB of virtual and 30m of residual memory).
My guess is that xCache's memory is included in the Virtual memory and reducing xCache size was just preventing it from hitting a user's maximum virtual memory size.
When changing the value in php.ini, all PHP processes had a fresh start, thus reducing the amount of virtual memory used and preventing and accounts from hitting the Cloudlinux user's 2GB limit.
If this is the case then it's the second incompatibility with CloudLinux. It would be great, concidering that most of your customers have cPanel + Cloudlinux + litespeed if you could work with them to get it fully compatible.
We're able to remove certain limits because we've got alot of memory but we're now down to disk and cpu limits knowing that whenever an account goes over his limit too much Litespeed doesn't detect the error correctly and forces a restart…
I've upped each accounts virtual memory limit to 4GB… I'll see if it happens again.