Re:Do Not Use Task Manager for Memory Info
by toast0 on Monday January 07, 2019 @10:59AM
(#18846214)
You can choose an overcommit policy on Linux, but most library developers on Linux have chosen the default and regularly allocate wide swaths they don't intend to use.
This is a real pain when moving an application from FreeBSD to Linux, as effective limits on memory are lost (ulimit set at ~90% of ram results in a malloc failure and a clean crashdump rather than death by thrashing, or an untrapable oom kill).
There could maybe be a middle ground where malloc would allocate large chunks of address space for ease of administration, and then ask the OS to commit those pages in smaller chunks as needed. Often, there's not much a lot you can do when allocation fails, but it's way more actionable if the failure is returned from a syscall vs failing when you write to an unbacked page, which could happen basically anywhere in your program.
This is a real pain when moving an application from FreeBSD to Linux, as effective limits on memory are lost (ulimit set at ~90% of ram results in a malloc failure and a clean crashdump rather than death by thrashing, or an untrapable oom kill).
There could maybe be a middle ground where malloc would allocate large chunks of address space for ease of administration, and then ask the OS to commit those pages in smaller chunks as needed. Often, there's not much a lot you can do when allocation fails, but it's way more actionable if the failure is returned from a syscall vs failing when you write to an unbacked page, which could happen basically anywhere in your program.