2007-08-14, 13:36 | Link #41 | |
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I found this wonderful quote on in a Newsgroup: "It is only when the actual memory usage exceeds the available RAM that it is necessary for the Memory Manager to identify inactive items in RAM that can be moved to the page file so that RAM can be used for other things. At that point some actual disk writing will occur and the performance slowed accordingly. But at that point the alternatives are such things as application or system crashes due to "out of memory" and I think almost anyone would prefer to see a little disk usage rather than that. " - http://groups.google.ca/group/micros...1785c5a45ce3dc It seems that there are quite a few theories on why Windows XP *must* have a page file. I suppose Linux/Unix systems are better in this area as they only use the swap when required. |
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2007-08-14, 23:58 | Link #44 |
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LOL @arcadeplayer987 & hobbes_fan
@matradley - Pre-allocation does ring a bell. I remember it is one of the reasons why disabling the swap file actually makes your memory usage less efficient. Since the OS needs to pre-allocate some memory, it means that without a swap file present, the OS will not use 100% of the memory as some of it has been reserved. Doesn't the nix type systems act like Windows setup in server mode and reserve all the memory for system usage? I guess it is to do with how the OS is setup.
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2007-08-15, 01:36 | Link #45 |
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For non critical systems like home pcs we should disable the swap file. The memory is cheap nowadays. Buy enough mem for your needs and disable the swap file. Is better to have ns access than ms access... besides you reduce the HDD activity by a lot!!!
Currently I have 2 GB of ram and since I don't use more than 1.7 GB I can turn off swap. No more unnecessary HDD writing. All stay in the ram. About the fragmentation. No matter what file system there will be always fragmentation. How much will it have? It depends on what activity is the HDD having. For example I think the best would be a program doing some sort of defrag whenever the computer is idle. Like putting all files contiguously in HDD maximizing the the free blocks. If there is a free block smaller than a X size then push the closest data to close that free block. That would assure you that your HDD would have the biggest free blocks whenever possible. Of course then your HDD activity would go sky high buy the count at the end of the day.
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2007-08-15, 03:23 | Link #46 | |
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And i don't think the way you mention about defrag would be effective. I thought the point of defrag is locating a file as close as possible. At your way you just closes gaps to make it look nice. But if your 500mb file is spreaded out to much, it will still have to move the thing up and down a lot to read it so you still lose performance/time. I think it has to move the complete file next to each other. Instead of grabbing for closes data that fits in the block.
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2007-08-15, 05:52 | Link #47 | ||
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2007-08-15, 05:57 | Link #48 | |
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Photoshop, however, is a bit different in the way it runs. I am not an expert with Photoshop, but it is among some of the few programs that can allocate 64-bit memory more efficient than most core Windows applications. |
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2007-08-15, 07:52 | Link #49 | |
Thinking outside the box
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And meh, guess some sites are sprouting nonsense than about photoshop not working. I still got my pagefile enabled though, i disabled it for a short time before, but since i didn't notice a difference i just enabled it again to be on the save side. But uhu since you mentioned not using swap files. Do you notice a performance gain? Or any advantage at all?
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2007-08-15, 08:24 | Link #50 | |
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2007-08-15, 09:00 | Link #51 | |
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2007-08-15, 09:09 | Link #52 | |
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And those things you mention grey_moon, you mean nand or those solid state harddisk or whatever there name is. I hope those become mainstream soon. Windows on one of those flash memories. And data on a normal hard disk. I just hate windows booting time. Saw a video of it somewhere. Windows booting in 15 seconds ready to use...
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2007-08-15, 10:55 | Link #53 | |
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http://www.nxsource.com/products/122...TE/GC_RAMDISK/ I remember chatting to some people about it in a linux expo. They were trying to come up with some method of "nuking" their hard drives for what ever reason. I pointed these out to them and said if you remove the battery then if any one powers it off for what ever reason it will be real hard to recover any of the data. *edit* Hee hee thinking about it, it is a solid state hard disk isnt it and the above example is a sata one and when I was reading up about them, they interfaced via the PCI slot.
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2007-08-15, 15:14 | Link #54 | |
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2007-08-15, 20:51 | Link #55 | |
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I have 2GB of RAM and I hit the swap pretty regularly (running OS X). Putting all the files close together would just mean those files will fragment as soon as you write anything additional to them. Thats why some Linux file systems (ext3) put space between files. Allows them to grow without fragmenting. This only really starts to break down when theres less than 10 or 20% free space. |
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2007-08-15, 21:37 | Link #56 |
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I'm not an expert in this subject...but I did stay at a Holiday Inn Express last night.
Joking aside, there are really a lot of misinformation in this thread. That said, I'm not citing sources for my assertions, either; I'm too lazy. Besides, there will be plenty other people eager to point out my mistakes, so anything not overturned is probably correct... First, no file system + free space allocation strategy could avoid fragmentation for all usage patterns. However, modern file systems are very good at reducing fragmentation, and modern OS are very good at reducing the impact of fragmented files. For example, leaving gaps between files instead of packing them tightly together may appear to promote fragmentation, but actually if you anticipate files to grow in size, then the gaps helps minimize fragmentation. In other words, unless you're using FAT, defragging HDs is a waste of time, not to mention precarious: what if power goes out in the process? Is even a 2x performance improvement worth risking your data? One scenario that almost always triggers the worse performance is when the disk is almost full, say 90%+. The idea is that you want the performance of the disk to be relatively independent of capacity filled, for most capacity ranges. That is, the performance curve when the disk is 0% ~ 70% full should be relatively flat. The tradeoff is that once you exceed certain threshold, performance drops off rapidly. Journaling file systems, in most cases, make no guarantee about the consistency of data. It's possible, although unlikely, that after a crash, many of your files your home directory become missing / corrupted. What won't happen is that two different files suddenly refers to the same sector on disk, or that the OS suddenly thinks your disk is twice (or half) its actual size. The goal of journaling is to maintain the consistency of the file system, because you can implement data consistency at "higher levels." It is possible to "push down" data consistency to the file system--there's a flag to do this for ext3--but the performance tradeoff is unfavorable. To the file system, data is just a stream of bytes, so to journal a write of "abcd" is to write "abcd" in the journal. Therefore, you are essentially writing two copies of the same data, and if that's really what you want, there are better approaches, such as RAID. OTOH, each application "knows" the structure to the data written, so it can leverage the knowledge to more efficiently implement data consistency. Now, on to swap files. Disabling swap files is a bad idea. Placing the swap file in a RAM disk is a worse idea. You are always better off having the OS manage memory for you: it's got more information to infer where the memory's needed than you do. Unless somehow you're force to use 32-bit XP--which has an effectively 3 GB memory limit--and want to utilize more RAM, leave the swap file alone. I'm not quite convinced that running Photoshop without swap leads to better performance. While PS effectively manage its own memory, without swap the OS can't page out unused background services to disk, thus less memory is available for PS. Alright, I think this rant has gone on long enough. EDIT: Others have beat me to some of the points I made to the post while I'm writing.
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Last edited by 052569; 2007-08-15 at 21:39. Reason: I type too slow. |
2007-08-15, 21:53 | Link #57 | |
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@052569 - Nice post
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2007-08-16, 01:01 | Link #58 | |
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If you never go over the total RAM you have why do you need the swap file? For example. You a few things opened. Now you go play a game a uses a considerable mem. Still in the overall it won't go over the total RAM you have. When you quit the game the system will be soooo slow coz it will be transferring from the swap the data of the other programs since the game ended so there is more free mem. This is 1 of the examples of what I hate the most. If you didn't have swap file there wouldn't be this unnecessary transfer.
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2007-08-16, 03:41 | Link #59 | ||
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I think a good analogy would be financial management. If you were born with a silver spoon, then there's no point in investing any of your money: you already have all that you'll ever need. For the rest of us who are less fortunate, keeping all the money in shoe boxes underneath our beds clearly isn't the soundest strategy. Investing some of that money will generally yield better returns. Now, is there a "best" investment strategy that will never fail? Whatever strategy you come up with, is it likely that it'll beat the one devised by teams of economists? Quote:
It's only recently that emphasis is put on interactivity over throughput. Obviously the latter is more important for servers, and computers has been servers far longer than "appliances." Going back to the money analogy, most investment plans assumes that you'll live until a certain age, say 75. If there's suddenly a plague that reduces the average lifespan to 45, then your investments become worthless as you'll not live to see it.
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2007-08-16, 03:47 | Link #60 |
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What if a program enters a loop or misbehaves in some other form? I've had my RAM sucked down to barely anything while the page file grew to gigabytes in size during instances like that. System slowdown was only fixable by terminating the program. If your RAM is exceeded (whether intentionally or not), is it recoverable, or do you get a blue screen/freeze? Depending on what you use your computer for, that might be an OK risk to take, of course. But for people who can't afford unscheduled reboots/downtime, a page file would provide a stability layer.
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