Gabriele Svelto (gabriele.svelto.delete@this.gmail.com) on January 20, 2020 7:02 am wrote:
> Michael S (already5chosen.delete@this.yahoo.com) on January 20, 2020 4:30 am wrote:
>
> > And quite likely "free physical memory" is wrong too, but if it's supposed to be the same
> > as "Physical Memory - Free" in 'Performance' tab of Win7 task manager then this number is
> > not particularly relevant anyway, because when system works as intended, majority of physical
> > memory is used by File system cache, i.e. not Free, but available on demand.
>
> That's the PhysicalAvailable entry of the PERFORMANCE_INFO field obtained via GetPerformanceInfo().
> According to Microsoft documentation that's the amount of physical memory immediately available w/o
> writing to disk. That should translate to free physical memory plus all the clean pages in the filesystem
> cache. I'm not sure what the task manager uses but they're most likely not the same measurements.

Microsoft has at least once (I think when Vista was released and also during Vista lifetime) changed what various free memory numbers in task manager mean. Quick googling turned up an article from early Vista days explaining how things are different compared to XP's Task Manager, but I'm pretty sure things change soon(ish) after that, because people didn't understand why Vista was always hogging all their precious physical memory.

I'd rather ignore Task Manager altogether. Every now and than I try to compare it's numbers to what Process Explorer (by Sysinternals, which is owned by Microsoft) shows, and it's pretty obvious that Task Manager is trying to be helpful for people who have no idea how memory management works. Nothing wrong with that, but don't try to use it as any kind of precision instrument.

-JLarja