Question "too much RAM?"

[GunsMadeAmericaFree]

I overheard my son telling a friend (while they were playing Minecraft) that the PC had "Too much RAM" yesterday.

I was sort of amused, because I've never considered any system to have "too much" memory.


However, are there any real world circumstances where a system's performance could be retarded by having huge amounts of RAM installed?

 

[Shmee]

Strictly speaking having more RAM itself isn't a cause for lower performance, however, higher capacity DIMMs generally aren't as high speed as lower capacity DIMMs can be, and having more memory can put more stress on the board, system, CPU, IMC etc, making memory overclocking or overclocking in general harder, with less headroom.

 

[mikeymikec]

I overheard my son telling a friend (while they were playing Minecraft) that the PC had "Too much RAM" yesterday.

I was sort of amused, because I've never considered any system to have "too much" memory.


However, are there any real world circumstances where a system's performance could be retarded by having huge amounts of RAM installed?

A bug in a game/app is a possibility I suppose?

As I understand it, some architectures do better with 2 modules than 4? Though I've never really looked into this.

The only other facet of "too much memory" is "you wasted tonnes of money on extra memory you'll never need".

 

[dave_the_nerd]

You need to have a conversation with your son. This is important.

You can never have too much RAM.

 

[VirtualLarry]

You need to have a conversation with your son. This is important.

You can never have too much RAM.

(*) Unless running Win9x-kernel OSes.

 

[carrotmania]

Why do you have 641KB of RAM?!

 

[kschendel]

I can think of two ways you can have "too much" RAM. One, already noted above, is if the memory controller doesn't deal well with the RAM configuration needed to have that much memory; e.g. 4 sticks of DDR5 vs 2. The other is rather theoretical: the OS needs memory to manage memory, and if you have way more than you need, the OS is wasting time traversing data structures for memory it isn't going to use. (If this is relevant at all, it's probably more so for servers that might have terabytes of RAM, not desktops with mere 100GB's of RAM.)

 

[DrMrLordX]

A long time ago, back when cacheable area was a thing:

Please explain "cacheable memory" to me \ VOGONS

www.vogons.org

sometimes having too much RAM was bad.

 

[igor_kavinski]

Could be due to garbage collection, if Minecraft does that. More RAM would lead to more RAM usage and hence more garbage collection to free data structures no longer in use.

 

[manly]

I can think of two ways you can have "too much" RAM. One, already noted above, is if the memory controller doesn't deal well with the RAM configuration needed to have that much memory; e.g. 4 sticks of DDR5 vs 2. The other is rather theoretical: the OS needs memory to manage memory, and if you have way more than you need, the OS is wasting time traversing data structures for memory it isn't going to use. (If this is relevant at all, it's probably more so for servers that might have terabytes of RAM, not desktops with mere 100GB's of RAM.)

That's not at all how memory management works. The OS works with a hardware MMU, so servers with many TB of RAM are no less efficient at memory access than small devices.

Memory management unit - Wikipedia

en.wikipedia.org

 

[Seba]

I overheard my son telling a friend (while they were playing Minecraft) that the PC had "Too much RAM" yesterday.

Ask your son why he said that.

 

[IronWing]

How can there be too much RAM? That is like saying there are too many flowers. - Mother Teresa

 

[kschendel]

That's not at all how memory management works. The OS works with a hardware MMU, so servers with many TB of RAM are no less efficient at memory access than small devices.

Memory management unit - Wikipedia

en.wikipedia.org

I think you misunderstand me. I'm not talking about hardware access. I'm talking about the data structures the OS needs so that it knows what each page of memory is doing; the "struct page" in linux, for instance. The more memory you have, the more there is for the OS to manage.

I doubt that there's a measurable effect in most cases, but theoretically, it's one way that too much RAM might slow things down.

 

[VirtualLarry]

The more memory you have, the more there is for the OS to manage.

Yep, memory management (on x86), is neither magical, nor free.

 

[manly]

I think you misunderstand me. I'm not talking about hardware access. I'm talking about the data structures the OS needs so that it knows what each page of memory is doing; the "struct page" in linux, for instance. The more memory you have, the more there is for the OS to manage.

I doubt that there's a measurable effect in most cases, but theoretically, it's one way that too much RAM might slow things down.

Sure, you said theoretically so I guess that's a reasonable caveat.

You said that Linux has to "traverse" the memory management data structures and that implies a certain inefficiency of operation. There is some "wastage" of RAM, but handling struct pages (as of 20 years ago) isn't a heavyweight operation AFAIK:

Mapping Addresses to a struct page | Page Table Management | InformIT

Linux handles the machine independent/dependent layer in a unique way, making page table management a bit tricky. Mel Gorman gives you the skinny on the process in this sample chapter.

www.informit.com

If you have any citations that this potentially reduces performance even a bit, I'm happy to read and learn!

 

[GunsMadeAmericaFree]

A bug in a game/app is a possibility I suppose?

As I understand it, some architectures do better with 2 modules than 4? Though I've never really looked into this.

The only other facet of "too much memory" is "you wasted tonnes of money on extra memory you'll never need".

Yep, what can I say? I saw a really good sale on 32GB of DDR4, (2 sticks) and boughtt it.

Is it WAY more than minecraft needs? Yes. Maybe that is what he meant when he said it to his friend.

Of course, I've had the 32GB for a couple of years now, and find myself occasionally thinking about putting 64GB in......

But then I realize, the 32GB is already 2,000 times what I had in my first computer, the good old TI 99/4a....

 

[VirtualLarry]

When you can get $55 or less 3200 DDR4 (Silicon power comes to mind) 32GB kit, getting 64GB is not unreasonable.

 

[manly]

But Minecraft runs on Java, so you need all of that 64GB and more.

/s

 

[nOOky]

I have 64GB of system memory, and it takes my computer much longer to boot probably due to the memory training going on. 32GB would probably boot up a lot faster, but I'm in no hurry. Note I don't actually think I'll ever need that much. I'd also buy a PCIE 5.0 NVME SSD if the price came down, just because. Because.

 

[Ken g6]

Yeah, bigger pickup trucks can have tradeoffs. Oh, wait, this isn't The Garage?

I once had a 486 that slowed down when I added an extra memory module. But it wouldn't run Netscape Navigator without it.

 

[igor_kavinski]

I once had a 486 that slowed down when I added an extra memory module. But it wouldn't run Netscape Navigator without it.

Couldn't afford a Pentium? I think a 486 was too slow for Windows 95. Unless you ran internet on Win3.1, which would've been very, very early on.

 

[Ken g6]

Couldn't afford a Pentium? I think a 486 was too slow for Windows 95. Unless you ran internet on Win3.1, which would've been very, very early on.

Yep, very, very early. Win 3.1 on a Packard Bell. I think it was a 4MB module, but I'm not sure.

 

[GunsMadeAmericaFree]

I have 64GB of system memory, and it takes my computer much longer to boot probably due to the memory training going on. 32GB would probably boot up a lot faster, but I'm in no hurry. Note I don't actually think I'll ever need that much. I'd also buy a PCIE 5.0 NVME SSD if the price came down, just because. Because.

I had never thought about it affecting the boot time. That is something that is going to have to be addressed as we get to 256 and 512 GB of RAM - we don't want the computers sitting there for 3 to 4 minutes on every bootup, checking for integrity......

 

[mikeymikec]

I have 64GB of system memory, and it takes my computer much longer to boot probably due to the memory training going on. 32GB would probably boot up a lot faster, but I'm in no hurry.

My PC spec: 7800X3D / ASUS TUF GAMING B650-PLUS / 32GB DDR5-6000 (DOCP) - takes about 30 seconds from power-on to POST. It's weird to think that my old Haswell build could present me with the desktop way faster than this PC.

 

[Pohemi]

As I understand it, some architectures do better with 2 modules than 4? Though I've never really looked into this.

The last time I ran into this on my own build was socket 939 nForce 3 chipset. System would not even boot with all 4x DIMM slots occupied.

The onboard memory controllers on those first AMD64 chips were notoriously touchy/buggy though. Not seen that happen since.

This wasn't a performance hit- it prevented the system from working at all.