Comment by jiggy2011 | Hacker News Reader

Comment by jiggy2011 | Hacker News Reader

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I would say that it's not so much that RAM Requirements are going through the roof as it is that the benefit you can get from having more RAM is going through the roof.

Having said that many of the languages we are using such as Javascript are not exactly storage efficient combined with combined with the fact that many people who would probably not have considered themselves "programmer" enough to write native apps in C++ back in the day are writing things in Javascript and putting them online.

I often see people "benchmark" things like operating systems or browsers based on RAM usage (people coming to the conclusion that 32bit Win XP is more "efficient" than Win7 for example) but I think it is far more important to measure swap file usage as this is the thing that actually hurts performance. Afaik there is no performance hit in overwriting a flip-flop in memory that already has a value stored but there is a huge penalty for hitting a disk. So I'd be quite happy to have all my RAM utilized all the time if I have 0 swapping.

First of all if you are using a 64bit platform your pointers are going to be twice as big as they used to be but you get to access so much more memory that this issue solves itself.

Also IIRC Windows 7 does things like arrange your frequently used data into a contiguous area of the disk and then reads all that stuff into VM at bootup. This will result in higher RAM usage (due to many pages being loaded into physical RAM) but better overall performance since if other stuff needs the RAM more urgently it can either swap the cache back to disk or overwrite the cache entirely.

Let's say you have 8GB of RAM and are watching a HD video which is 7GB uncompressed and the rest of your system only really needs 1GB of your RAM, surely it makes sense what whilst you are watching the video you can use spare CPU cores to uncompress the rest of the video and put it into RAM.

I think it's more the case that computing will always expand to fill the amount of memory available. Bearing in mind that even the cost of swapping is dramatically reducing with SSDs etc.

> Let's say you have 8GB of RAM and are watching a HD video which is 7GB uncompressed and the rest of your system only really needs 1GB of your RAM, surely it makes sense what whilst you are watching the video you can use spare CPU cores to uncompress the rest of the video and put it into RAM

It makes a ton of sense for all those people (and other species, from different time/space geometries) who can comprehend a movie by experiencing its time dimension as a single event. Ordinary humans may find it less useful, albeit having no delay when skipping back and forth may have some utility for those of us who experience time in a more traditional way ;-)

Let's say you have 8GB of RAM and are watching a HD video which is 7GB uncompressed and the rest of your system only really needs 1GB of your RAM, surely it makes sense what whilst you are watching the video you can use spare CPU cores to uncompress the rest of the video and put it into RAM.

That's not clear to me. Why do something ahead of time that can be done faster than needed on the fly anyway? You're basically assuming that when system resources are needed for something else halfway through your video, processing power will be more useful than space.

True , with video decompression that is probably the case.

I'm sure there are lots of examples where doing complex calculations whenever you have CPU spare and swapping them out to disk as needed would be preferable to having to contend with whatever else needs to use it at the time.

I think the key is how to OS deals with memory contention issues rather than just minimizing memory usage.

Someone with a better understanding of OSes than me could probably clarify.

I guess the performance hit is when you write a page of RAM to the disk, perhaps there are some cases where you don't bother to do this if memory contention is high?

Really, you don't want to randomly waste cpu cycles for nothing, like pre-decompresssing video. It just increases the power usage and heat of the computer. It would also make it harder to skip, since the program needs to finish the portion it is working on.

One thing people often don't realise is there isn't really 'wasted' RAM, your OS usually uses the rest to cache things, especially files. File caching can greatly speed up disc reads and writes. (The following only applies to linux, I'm not sure about other OS's; all three have very different memory models). When memory is getting high, a few things can happen (depending on whether you have swap). The file cache is preferentially cleared first, but swapping pages to disc is also considered readily. An interesting thing is that swapped pages aren't deleted from swap straight away, only if they are modified (so swap usually doesn't decrease in size). There is also the Out Of Memory killer, which can kill applications using too much memory. It really is an interesting area. You can read more from this page http://tldp.org/LDP/tlk/mm/memory.html. Just remember all OS's are different.

If you can spin up the HD, read the file into RAM, and spin down the HD, it will take a lot less energy than reading the file slowly over the course of an hour.

Spinning down the hard drive is a pretty bad idea as it doesn't save much power & there is usually a noticeable lag to spinning it back up again. Also most applications & OSes these days expect it to be always on. Your carefully crafted scenario goes up in smoke if your OS likes to log stuff, your browser wants to dump it's cache or your word processor wants to autosave.

That example isn't really good, but think back to the original post: if your browser caches every element of every already rendered page, it can be super fast in case of a page reload/tab reopen.

You can only store about 20 minutes worth of decompressed RGB24 1080p video in 7GB of RAM. There really is no point to doing this.

The only time this would make sense is in a content creation environment where quick access to uncompressed frames makes a difference. However, those environments are already CPU starved. Typical consumers would not see a benefit from this scenario. More benefit will be had with the transition to SSDs, they will be eventually be much much faster & require less power than current hard drives.

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