Benefit of more RAM

Osiris · 2012-03-07 20:01:54

Hello,

My current desktop system (Quad Phenom II 3,4GHz, / on SSD, /home on HDD) is equipped with 8 GB RAM and no swap. I'm thinking about upgrading to 16GB of RAM. Reason is mainly some memory hungry CFD post-processing software I want to run. I wonder how the rest of the system would benefit from this upgrade? Will the system benefit from the larger disk caches etc. or will be there no effect at all? (KDE is my desktop environment)

Thx!

karol · 2012-03-07 20:09:00

Are you maxing out RAM with KDE? If not, it probably won't matter if you add more RAM.

Osiris · 2012-03-07 20:11:02

Maxing out regarding the actually used memory by applications, no! But since linux uses the spare memory for caches e.g. it might still have an effect.

Gcool · 2012-03-07 20:24:20

It will largely depend on how much memory your "CFD post-processing software" will be eating up. If that usage combined with the general linux usage (caching memory as you said) does not reach 8Gb in total; there's little use in upgrading.

karol · 2012-03-07 20:25:26

You are using SSD for / so I'm not sure if there will be a noticeable improvement in e.g. system responsiveness but RAM is cheap nowadays so getting more of it (if the board supports it) shouldn't be a problem.

lagagnon · 2012-03-07 20:32:45

Have you actually analyzed the output of "free" when you are running the apps you want? What does it tell you? Particularly, if you have quite a bit of free -/+ bufferers/cache RAM remaining then adding more RAM will not benefit your system.

Osiris · 2012-03-07 20:42:34

As I said, there is absolutely no memory shortage when running the usual desktop applications, but there definitely is when running the CFD stuff. I wonder if the additional disk caches have any real effect.

meph · 2012-03-07 22:23:20

Osiris wrote:

Maxing out regarding the actually used memory by applications, no! But since linux uses the spare memory for caches e.g. it might still have an effect.

When you're not using your memory heavy software you're not getting anywhere near 8 GB (cache included), and when you're actually using it I doubt that you give a damn about cache. Theoretically what you described is correct, but since you already have 8 GB's, then I doubt increasing it any further would have any real effect. It would be much more noticeable if you had say 2 GB's and were considering upgrading to 4 GB, even if you weren't regurarly using all of your 2 GB. So my advice would be to get more RAM only if you actually need it, i.e. if you're regurarly running out while using your CFD software.

karol wrote:

You are using SSD for / so I'm not sure if there will be a noticeable improvement in e.g. system responsiveness but RAM is cheap nowadays so getting more of it (if the board supports it) shouldn't be a problem.

Why SSD, you're thinking about heavy swapping? While they're fast, SSD transfer rates still can't be compared to DDR3 speed. Moreover, while I consider the panic around poor SSD longevity (limited write cycles in particular) largely exaggerated, it is still based on truth, and a lot of swapping is one thing you want to avoid.
edit: meh scratch that, I misread your post. Swap is not what you meant, but still might be a thing to consider.

Last edited by meph (2012-03-07 22:25:04)

jac · 2012-03-07 22:58:23

meph wrote:

When you're not using your memory heavy software you're not getting anywhere near 8 GB (cache included)

I realize I'm not your average case, but I typically max out all of my 16 GiB with ext4 inode cache... Depending on Osiris's needs, he may also be hitting the limit with cache.

@Osiris: even with the added room for cache, I don't really notice a difference between my desktop and laptop (16 vs 8 GiBs). Though, allowing the ext cache to grow it does seem to help with the non-SSD drives in my desktop. I've never measured it, though, so take it with a grain of salt.

meph · 2012-03-08 06:50:35

jac wrote:

meph wrote:
When you're not using your memory heavy software you're not getting anywhere near 8 GB (cache included)
I realize I'm not your average case, but I typically max out all of my 16 GiB with ext4 inode cache... Depending on Osiris's needs, he may also be hitting the limit with cache.

Indeed, everyone's mileage may vary. In general, from my experience, the more RAM you already have the lesser is your benefit from further increasing it, but it all depends on how your system is being used.

Arch Linux

#1 2012-03-07 20:01:54

Benefit of more RAM

#2 2012-03-07 20:09:00

Re: Benefit of more RAM

#3 2012-03-07 20:11:02

Re: Benefit of more RAM

#4 2012-03-07 20:24:20

Re: Benefit of more RAM

#5 2012-03-07 20:25:26

Re: Benefit of more RAM

#6 2012-03-07 20:32:45

Re: Benefit of more RAM

#7 2012-03-07 20:42:34

Re: Benefit of more RAM

#8 2012-03-07 22:23:20

Re: Benefit of more RAM

#9 2012-03-07 22:58:23

Re: Benefit of more RAM

#10 2012-03-08 06:50:35

Re: Benefit of more RAM

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