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Ars Analysis Calls Windows 7 Memory Usage Claims "Scaremongering"
Via newsycombinator comes a reaction at Ars Technica to the recently reported claims of excessive memory use on machines running Windows 7. From the article: "I installed the XPnet performance monitoring tool and waited for it to upload my data to see what it might be complaining about. The cause of the problem was immediately apparent. It's no secret that Windows 7, just like Windows Vista before it, includes aggressive disk caching. The SuperFetch technology causes Windows to preload certain data if the OS detects that it is used regularly, even if there is no specific need for it at any given moment. Though SuperFetch is a little less aggressive in Windows 7, it will still use a substantial amount of memory—but with an important proviso. The OS will only use memory for cache when there is no other demand for that memory."
Though SuperFetch is a little less aggressive in Windows 7, it will still use a substantial amount of memory—but with an important proviso. The OS will only use memory for cache when there is no other demand for that memory.
I really wonder when people will get this. In the earlier thread I saw people commenting that Windows 95 didn't need so much memory and so on..
To state it again. This is not RAM memory you need, use or have purpose for. IF you do need it, it is zeroed-out and free'd to application in like 30ms (one frame in usual FPS games).
If you have fast memory, do use it to it's full extend.
I think it's just a sign of the times. I regularly bump up against my 2GB ram limit (once a day) if I have GIMP/Photoshop open, 3 or 4 Chrome windows open with 10-20 tabs each (many of those being youtube videos), usually a videogame in the background (Windowed No Border mode at full or almost full screen resolution rules), along with whatever else I'm doing, a paused VLC video, steam, and any other background apps + whatever I'm working on currently. This isn't a problem in Win7, it's a problem of Leaving a Bunch of Shit open all the time.
moox. for a new generation.
It's not "hogging" memory if it dumps it the second you start up a program that needs it... It also doesn't make your system "appear" faster, it makes it faster. I paid for all that RAM, I don't mind it being taken advantage of; that's why it's there in the first place...
Linux uses available memory for cache, and rather aggressively. All available memory can be filled with cached file blocks. This happens routinely on systems which have big randomly-accessed files open, like databases.
There's nothing wrong with this, except that, once in a while, Linux hits a race condition in prune_one_dentry, causing an "oops" crash, when there's an unblockable need for a memory page and something is locking the file block cache.
This is one of the Great Unsolved Mysteries of Linux. Linus wrote about it in 2001 ("I'll try to think about it some more, but I'd love to have more reports to go on to try to find a pattern.. "). As of 2009, this area is still giving trouble. The locking in this area is very complex.
If one byte takes 10^-9 s, a million bytes take 10^3 s.
Only if you do them one at a time, one after another, waiting till each had been cleared. That'd be... Wait this is Microsoft we're talking about here... Carry on.
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Windows 7 is sucking up your system memory to make Windows appear faster.
So windows has a feature which makes everything run faster and yet it only "makes Windows appear faster", instead of making it actually faster?
It seems to me that windows is only using hardware in a rather intelligent way: if it's not being otherwise used or needed, it uses it to boost performance.
Linux does the same thing, as far as I know, and you don't see anybody calling Linux a memory hogging OS.
Everyone knows there's a shadow-bus on the motherboard that only open source operating systems have access to.
Describing caching as a way Windows makes your computer "appear" faster is really a little disingenuous. If that is the only metric for your complaint then you should be angry that your processor caches as well. After all, your processor takes the time to check two or three caches every time it issues a move instruction. If it misses every time, then it has to pick what to throw out of the cache and read directly from memory. Wouldn't it be so much better if it just made a fetch to ram every time there was a move instruction? After all, your processors caches only "appear" to make your processor faster right? The question that people should be asking if they want to get upset about SuperFetch is does this approach to ram use benefit the user enough to be worth the extra complexity in the operating system's memory allocator.
People always mix up Sweden and Swindon
rewriting history since 2109
if everyone is so afraid of their computer memory being used to the fullest, why do these people install so much of it?
I've got 8GB of ram in the machine I'm on at the moment, and I want the OS and applications to use it to the fullest and most efficient extent possible at all times. I didn't install a 64-bit OS and 8GB of ram so that I can see 6GB free at all times.
I want a new quote. One that won't spill. One that don't cost too much. Or come in a pill.
If Windows 7 actually uses that much memory it's not scaremongering, it's memory hogging. Whether it's using it on not is a pretty fine distinction, it's still using it just because it can. If something else needs it, Windows has to decide if it wants to let go of it or not.
So are you saying Linux, BSD, Mac OS X and pretty much every other modern desktop OS other than Windows XP are also memory hogs as well? Because they also do the exact same thing and use up all of the free memory for caching, marking it as available.
You might want to grab a copy of Process Explorer sometime, and look at the stats it reports. you'll notice that windows actually spends idle time pre-zeroing ram, so that this is already done, in more than enough amounts. If your system is slammed, i could see having to pre-zero the pages, just before use, however, but it's not like it's not something that couldn't be done while waiting for other I/O operations to complete (since your system is slammed anyway :) )
My laptop currently has 2.8 million pages zeroed atm (it has 8gb, and I don't have much running right now, so there's not a lot to cache.)
The only data in the article you refer to was captured data from XPnet that said that >90% of RAM was in use in Windows 7 machines. There was no data saying it led to swapping, that was supposition.
http://www.computerworld.com/s/article/9158258/Most_Windows_7_PCs_max_out_memory
http://lkml.org/lkml/2005/8/20/95
fflush() just flushes stdio's buffer, so that any data written to the file is sent to the operating system (via write() on *nix), making it visible to other programs. It does not flush anything in the operating system's own buffers/caches. Also, fclose() calls fflush() automatically, so calling both is redundant.
You're probably thinking of fsync(), a system call that does actually force data to disk. And should almost never be used, unless you enjoy waiting through several seconds of disk grinding and general unresponsiveness.
Not necessarily. Many programs commit large chunks of memory in case they need it later but only use a small portion initially. This simplifies program logic because you don't have to free and reallocate the buffer when you need more space, deal with potential reallocation failures etc. Or a program might want to specify a larger-than-default stack commit size to make sure it doesn't hit a stack overflow if it tries to extend the stack while the system is temporarily out of commit (most services and other system critical processes do that). Or it might map a copy-on-write view of a file, in which case commit is charged for the entire view but no extra physical memory is used until the program actually writes to the pages. Etc etc... The end result of this is that you can't really say anything conclusive about physical memory usage by looking at commit charge
Commit charge is a virtual memory metric. It's great for detecting memory leaks and deciding how big your pagefile needs to be, but not so great for understanding physical memory usage. Often it might seem like there is a correlation between commit charge and physical memory, but you can also find systems that are very low on available RAM yet have plenty of available commit, and vice versa.
Task manager now shows used physical memory (defined as Total - Available). Available memory is the most straightforward way to understand whether your system needs more memory or not, and this is why in Vista/Win7 it was chosen as the main indicator of "memory usage".
I didn't make a snide remark. I pointed out that windows maintains a pool of zeroed ram, and will constantly fill it when it's able to.
Windows will allocate from that pool first, and then top it back up when it hits a threshold of low free memory from supercache.
It then has the luxury of handling this in the background, so you're not waiting for the system to zero memory out, unless you somehow manage to totally max out the memory you've got in use.
It's at this point when you've got bigger problems, like the fact that the disk will probably become your bottleneck, not the speed at which you can zero out ram.
I didn't miss your point, I'm suggesting that you're not thinking like an operating system designer, and saying "how can i shorten the critical path of giving a process the memory it requests?" The answer is: Pre-zero memory, and fill the zeroed pool from the cache as needed when you get low. There's no "wait" for zeroed out memory, at this point.