86% of Windows 7 PCs Maxing Out Memory

CWmike writes "Citing data from Devil Mountain Software's community-based Exo.performance.network (XPnet), Craig Barth, the company's chief technology officer, said that new metrics reveal an unsettling trend. On average, 86% of Windows 7 machines in the XPnet pool are regularly consuming 90%-95% of their available RAM, resulting in slow-downs as the systems were forced to increasingly turn to disk-based virtual memory to handle tasks. The 86% mark for Windows 7 is more than twice the average number of Windows XP machines that run at the memory 'saturation' point, and this comes despite more RAM being available on most Windows 7 machines. 'This is alarming,' Barth said of Windows 7 machines' resource consumption. 'For the OS to be pushing the hardware limits this quickly is amazing. Windows 7 is not the lean, mean version of Vista that you may think it is.'"

Comments

When do people get this

[sopssa]

RAM is wasted when it isn't in use. The fact that the task manager in Windows says your RAM is used 95% tells nothing, and no it won't "result in slow-downs as the systems were forced to increasingly turn to disk-based virtual memory to handle tasks". I'm actually really surprised, and not in a good way, that "chief technology officer" of the company doesn't know this.

The new memory models in recent OS's try to utilize all the available RAM (as they should) to speed up things otherwise. It makes a lot of sense to cache things from hard-drive in low-peak usage points, and in such such way that it doesn't interfere with other perfomance. When the things that are most often used are already cached in RAM, their loading works a lot faster. This doesn't include only files, icons or such, but everything the OS could use or do that takes time.

If theres a sudden need for more RAM, the cached data can be "dropped" in no time. It doesn't matter if it averages at 25% or 95%, just that the perfomance overally is better when you utilize all the resources you can to speed up things in general.

Re:When do people get this

[Mr Thinly Sliced]

My understanding was that memory used for disk caching doesn't show up in task manager as "used".

It's been a while since I booted win7 though, so I might be mistaken.

Certainly under linux ram used as disk cache is marked "free".

It wouldn't surprise me that win7 has a heavier memory footprint though - as more applications move to .net and web browsers use lots of flash / silverlight etc - all of these things have a RAM cost.

Re:When do people get this

[Sockatume]

If they'd measured pagefaults, they could've reported pagefaults. They didn't. RAM usage appears to be the total basis for the article, so his concern is a genuine one. We don't know enough about the study at this stage to dismiss it.

Re:When do people get this

[snemarch]

It shows up as part of the memory commit bar - which is what regular users will look at, and then go off screaming about "OMG IT USES ALL MY SYSTEM MEMORY!1!!! one one". It's also deducted from the "free" count, since technically it isn't free (it can be freed quickly, but has to be zeroed out before it can be handed off to a new app - security and all).

The Win7 task manager does show a "cached" stat, though, so your effectively free memory is "free"+"cached". And if you want more comprehensive memory stats, you should look at perfmon.msc or SysInternals' Process Explorer.

I wonder if TFA has actually measured that disk swapping happens (easy with procexp or perfmon), or are just shouting their heads off without understanding what's going on... it's well-known that SuperFetch utilizes otherwise unused memory for disk caching, and does so proactively :)

Re:When do people get this

[Moryath]

You obviously don't understand memory access design. It's all about feeding the CPU. There are two sorts of relationships we can use to make this work: temporal and sequential.

Hard drives are the largest-capacity storage (well unless you want to go to tape). But they're slow. Even the fastest high-RPM SCSI or SATA drives are SLOW compared to what's above them. This is mitigated, somewhat, by putting some cache memory on the drive's controller board itself. Still, having to "hit" the hard drive for information is, as you say, a slowdown. Same goes for "external" storage (Optical media, USB media, etc).

So you try to keep as much information as possible in RAM (next step up). Hitting RAM is less expensive than hitting the H/D in terms of a performance hit. In the original days of computing (up until the 486DX line for Intel CPUs), RAM and CPU operated on a 1:1 clock speed match, so that was that.

Once you factor in the "clock multiplier" of later CPU's, even the fastest RAM available today can't keep from "starving" the CPU. So we add in cache - L3, L2, and L1. the 486 implemented 8KB (yeah a whole 8K, wow!) in order to keep itself from starving. L3 is the "slowest", but largest, L2 is faster still but smaller, and L1's the smallest of all, but the fastest because it is literally on the same die as the CPU. That distinction is important, and in general you'll find that a "slower" CPU with more L1 Cache will benchmark better than a "faster" CPU with less.

The CPU looks for what it wants as follows:
- I want something. Is it in L1? Nope.
- Is it in L2? Nope.
- Is it in L3? Nope.
- Is it in RAM? Nope.
- Is it in the H/D Cache? (helps avoid spin-up and seek times) Nope.
- Crap, it's on the H/D. Big performance hit.

Everything except for the L1 check, technically, was a performance it. The reason for pre-caching things (based on temporal and sequential relationships) is all about predicting and getting what will be needed next into the fastest available place.

Yes, I suppose you can run an entire system where it all goes into "RAM", and you'll see it as "more responsive" simply because you never have to touch the hard drive. But turning off HDD caching is a BAD idea. It makes cache misses that much more expensive because then, instead of having even the chance of finding what you needed in RAM or in the HD's onboard cache, you have to wait for the H/D to spin up and seek to the right sector.

Re:When do people get this

[TheLink]

Yeah I don't know why they don't set up the counter by default.

Anyway to set it up yourself:

Start perfmon.msc
Then add counters
go to Memory, add "Pages Output/sec".

I'm not an authority on virtual memory but from what I know:
Page Faults/sec is not usually relevant for this - the virtual memory stuff will have page fault even if it's not swapping to/from disk - it's part of how virtual memory works.
Page Inputs/sec could happen when you launch programs (then the O/S starts paging in the stuff it needs) - it's no indication of running out of memory.
Page Output/sec on the other hand is when the O/S is low and needs to copy stuff in RAM and write it OUT to disk so that it can reuse that RAM for something else. This is the one you want to monitor.

Parent is +1 informative

[Anonymous Coward]

You cannot study virtual memory performance without considering how many page faults occur.

It is perfectly reasonable to use RAM as a filesystem cache, which is why Linux has adopted this approach. The effect is that almost all of the physical RAM is always in use. The cost is that pages are more likely to be wrongly swapped out - however, in typical cases, this increased cost is tiny in relation to the huge reduction in the number of disk accesses.