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VulcanB2
Chief Pilot Joined: 02 Apr 2008 Points: 13365 |
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Posted: 12 Jun 2009 at 4:55pm |
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Strangely enough, I did get Process Viewer - apparently it could release all file handles without terminating the holding process.
There is one secret weapon in the arsenal I did consider: Windows File Permissions. Take your favorite app, and deny access to it whilst it is running. It will prevent the process from coming back to the file later (if it ever should). Next best thing to deleting it. Best regards, Vulcan. |
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MartinW
Moderator in Command Joined: 31 Mar 2008 Location: United Kingdom Points: 26722 |
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Magic... run away quick, change the subject, anything, but don't dwell.
If you like I'll set up a diversion, 9/11 perhaps?
Edit: I've diverted him with talk of dinosaurs, lost worlds etc, in another topic.
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Magic Man
Chief Pilot Joined: 02 Apr 2008 Location: South Wales Points: 5336 |
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To be fair to our pointy friend, whilst looking for the backup stuff for this, it's clear that just like in any other subject misonceptions can quickly take hold and spread far and wide. There was a suprising amount of stuff on technical sites that got it wrong as well and they were meant to be the experts advising others.
Not sure if anyone else is interested but during my trawls came across the little tool available here... http://www.tmurgent.com/Tool_ATM.aspx - which gives a great view of what is going on in your PCs memory.
To come back to a 'issue' mentioned in the past by others (and one in particular who will remain anonymous... ) regarding Vista being a memory hog, using all the memory etc. to which the usual reply has become, "its designed to use all the memory it can, unused memory is wasted memory" etc. - this tool shows that very nicely. Reboot etc. and you'll see the precache stuff empty, slowly filling up as it does it's stuff, caching stuff it thinks you'll use based on past experience. If you need that memory for anything else, it'll just dump it out.
Which ones? No, second thoughts, don't answer that...
( no really, don't answer that... group hug instead)
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[deep voice]"Windows - the memory manager conspiracy" a Slim Martin production.[/deep voice]
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MartinW
Moderator in Command Joined: 31 Mar 2008 Location: United Kingdom Points: 26722 |
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Game set and match to magic then?
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VulcanB2
Chief Pilot Joined: 02 Apr 2008 Points: 13365 |
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I assumed nothing, and did try it. This is why it can't be deleted: http://en.wikipedia.org/wiki/Memory-mapped_file#Platform_support Been a damn long time since I read about this. http://msdn.microsoft.com/en-us/library/ms810613.aspx Holy cow - I was hardly 11 years old when I last read about this (1993). FYI I've been doing this stuff since I was 4 (I started out on a System 19 - that is One Nine - writing machine code, then moved to the Motorola 6800 before I got my first PC). I thought MMF went out back then. Didn't realize they were still using it. I never use it - thought it was depricated (back in 1995 to give you an idea - when Win 95 was released to be exact). I've only thought this for a mere 16 years. When they introduced the swap file in Win 3.x, I thought it was the replacement and MMF was simply for backwards compatibility. Those were the days!! I've been bashing my head against the wall for years trying to figure out why that ****ing file won't delete when an app is running, yet you could read it. Never thought it was this method of access that was behind it (I was that convinced it was depricated). Note carefully that the article says that all 6 memory access methods are totally independent of each other. On this point I raise my hand and say "I'm wrong". I did quote sources though. Always important. I'm , seriously. I still stand by my other comments though. O/T: Still got one of these in the loft: http://en.wikipedia.org/wiki/KIM-1 ...and I still use one of these! http://en.wikipedia.org/wiki/MEK6800D2 Damn good processor. FYI the group of 4 LEDSs are the memory address, and the group of two on the right are the data/instruction as necessary. They are split like this for easier reading whilst debugging. 0A - LOAD A 03 - DATA 0B - LOAD B 23 - DATA 1C - ACC A + ACC B -> ACC A 3F - HALT I think that is correct. Load accumulator A with "03", load accumulator B with "23" sum the two and store in accumulator A. By looking in accumulator A I should have the value "26" (remembering it is HEX!!!!!). Best regards, Vulcan. |
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Magic Man
Chief Pilot Joined: 02 Apr 2008 Location: South Wales Points: 5336 |
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You are talking rubbish again I'm afraid. There is nothing really to understand about rubbish that I am not getting. Again, stop skirting around the edge, your whole point was that it is somehow better to run without a page file under real conditions (not your imaginary unlimited memory scenario) which is why you switched it off. You are just posting diversionary fluff. Okay, let's go back to the "point [you are] making" and that I apparently don't understand. Your experiment to show and prove that "the system does not care if the file is on disk or not". You stated...
Except, in reality, you never did delete the FS9.exe when it was running did you? You just assumed that moving it or renaming it would prove the same point. Because (as I wondered earlier and later found out and verified myself) there is no worry about what happens with the pager trying to access this file that no longer exists because you are prevented from deleting the file in the first place. Try it this time rather than assuming - you'll get a big fat dialog... "Cannot delete FS9: Access denied" Reason why there are no issues when you move it or rename it is because the OS keeps tracks of the file so remains able to page out memory relating to it and page it back in from the file if required. FS9.exe was still "backed by a file on the HD" as I put it all along... Now, let's move on to your issue with the fact that memory pages that are backed, i.e. those that have come directly from the hd in the form of an .exe (your fs9.exe for example) or .dlls etc are freed if required and then paged back in directly from the file. I have explained this several times. In response to those explanations you have stated...
Okay, here we go then, how about...
and...
and...
and...
From where? Microsoft Developer Network. http://msdn.microsoft.com/en-us/library/ms810613.aspx - memory mapped files. You should take a look. Also points out the benefits of using a page file for sharing data between processes which can prevent "a waste of system resources". Nice big diagrams as well showing the page file as a key part of the overall memory management - strange that if it's not really that important and not needed as you say... Also...
Same library, section detailing the virtual memory manager in Windows NT.
Strange, nothing there about the performance benefits of disabling the page file though... Just to close with a few of your own statements...
I think we should call it a day there shouldn't we... Apologies to all others for this and all the quotes here etc. Normal service will be resumed shortly... |
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VulcanB2
Chief Pilot Joined: 02 Apr 2008 Points: 13365 |
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The point I am making, and you don't understand, is that the system does not care if the file is on disk or not. It has no bearing on memory and whether the system will try to page it out or not. Clearly you're never going to understand this.
Huh? Read my links again. Keep reading until you understand. I'm finished here. Best regards, Vulcan. |
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Magic Man
Chief Pilot Joined: 02 Apr 2008 Location: South Wales Points: 5336 |
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[pantomime audience]Oh yes it is…[/pantomime audience]
What exactly did you demonstrate and conclude from this and how is this trying to prove your case that a page file isn't needed...? Loading it and then removing the physical file is only going to cause a problem if the situation arises that the virtual memory manager decides to drop memory pages relating to FS9.exe and then tries to page them back in. Actually, since the file no longer exists I’m not sure if the pager will even permit those code pages to be released or, if a pagefile is present, whether it instead uses it for backing store of the pages moved out.
Rubbish. Unbacked pages will have no physical reference because they don’t exist on disk. Backed pages will have since their pages are paged in from the .exe, .dll file etc. It obviously knows where it came from. Or are you saying that all memory pages that are paged out go to the pagefile? If so then that is wrong and if so then where are you without a pagefile since in your world you would never be able to page anything out. You've already correctly said that paging still occurs without a page file, in your world how can it if "All it does when it writes to the page file to clear some physical memory, is copy the memory location verbatim"...?
You have a flawed understanding (sorry, left the quotes off that...)
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VulcanB2
Chief Pilot Joined: 02 Apr 2008 Points: 13365 |
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No it isn't. Not at all. Please refer back to my link to the slides from the Carnagie Mellon University website. As I demonstrated when I deleted the FS9.exe file - the file was no longer on disk for this behavior to work. If this is how it did work, deleting the FS9.exe file should have created chaos, regardless of whether the swap file existed or not. As should be clearly apparent to you by now, no reference is ever kept of which file data came from. The system doesn't know, and it doesn't care. All it does when it writes to the page file to clear some physical memory, is copy the memory location verbatim. That's it. What occurs to files on disk, it doesn't care. Again, please study the link very carefully. You have a flawed understanding. Best regards, Vulcan. |
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Magic Man
Chief Pilot Joined: 02 Apr 2008 Location: South Wales Points: 5336 |
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If the memory manager decides to release memory pages occupied by code that is backed, i.e. .exe’s, .dll’s, etc., stuff that already exists on the disk, then yes it is just freed, unless the page has changed, there is no need to copy it to a page file (why would it need to, it already exists). When that page is required again it is simply paged back in, i.e. re-read from the file on disk, i.e. from the .exe, .dll etc.
Absolutely astounding logic there... “Well Mr President, the reason I pushed the big red button with ‘Do not push’ printed on it was because it didn’t say it would cause any harm...”
Winner of the grand prize in the ultimate copout competition 2009. Explanation of theory by reference to an unobtainable quantity, brilliant!
Your whole point was that you have disabled your page file because it is beneficial, not because in a hypothetical situation with unlimited memory. You haven't got unlimited memory. It's irrelevant anyway since if you did have unlimited memory then the mm would never need to page out unbacked store to the page file anyway so it wouldn't be used. Turning it off would gain nothing other than recover the small amount of drive space - and in this hypothetical world of unlimited memory then surely we have unlimited drive space as well so why bother?...
You do not have plenty of physical memory. 4GB was enormous and certainly more than plenty in most cases a few years ago, now it’s average. The more we have the more we use, you can never really have plenty...
Reducing the memory managers options does not increase performance. The page file will only be used if the memory manager needs to use it, if it needs to use it then you need a page file. Without it you are limiting its options.
And disk space is even cheaper. There is absolutely no excuse not to use a page file if you regularly run out of physical memory, buying extra RAM is a second option limited by funds and, if you are running a 32bit OS, limited by the addressable range. As said, 4GB is not that large. Go with it by all means, I have 4GB in my main box, but why then not give yourself the additional use of a page file for the mm to use if it requires it?
On a 32bit OS a single page file is ‘limited’ by that size by default. It can be made larger as Marmite noted. You can also have additional page files on distinct drives (I have one on each of my two drives). You can also have multiple page files on the same drive (different directories) with a registry edit.
It will use them as it sees fit. It will choose which to use based on I/O metrics for best performance.
Thanks for that, wasn’t in question. “Nothing to do with it” is a but extreme though, they are obviously related. |
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Marmite
Chief Pilot Joined: 11 Apr 2008 Points: 1029 |
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Figure came from a technet article http://technet.microsoft.com/en-us/magazine/2007.04.desktopfiles.aspx
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VulcanB2
Chief Pilot Joined: 02 Apr 2008 Points: 13365 |
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That's stupid. You'd have to have 4096 page files to make use of that!!!
Best regards, Vulcan. |
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Marmite
Chief Pilot Joined: 11 Apr 2008 Points: 1029 |
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The page file size limit for 32bit Windows (with PAE enabled, which most XP are by default) is 16TB.
I'd rather leave my paging turned on, than risk BSODs and system crashes over a slight possible performance increase (not that I've seen any figures that prove such an increase exists). |
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VulcanB2
Chief Pilot Joined: 02 Apr 2008 Points: 13365 |
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Yes, if you run out of physical memory. If you have plenty of physical memory, then disabling the swap file is not a problem. Further, it increases performance because like it or not, even if there is free physical memory (several hundred megabytes) Windows will still copy memory to the swap file!!! The result of this is if the system then tries to access memory that was swapped out, even if it is for 10 bytes, it has to make disk I/O and performance instantly suffers.
Only if you were stupid to try and run the system to the limits and beyond. Memory is so cheap there is no excuse not to add more physical RAM if you regularly run out of physical memory (swap file enabled or not). You WILL see increased performance for doing so. It is best to have more memory than you will use (hence my choice to go for 4 Gb for Vista for example - I know I won't use more than this at the current time. If I do, I'll simply buy more RAM). Some limitations: 32-bit OS can never ever address more than 4Gb of memory. Because of memory mapped I/O present in current computer systems that you or I run, this limit is further decreased (in my case, to 2.6 Gb as the rest of the upper address lines are used for addressing hardware, etc. and are unavailable for memory addressing). The page file can not exceed 4096 Mb in size, and XP x86 will never acknowledge more than 4 Gb of physical memory. Here is a question: if you have two page files, both 4096 Mb in size, will Windows use them up to the full 8 Gb available? From your link: http://support.microsoft.com/kb/555223 Let me clarify one important point: Virtual memory is NOT the page file. It has nothing to do with it. Best regards, Vulcan. |
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Marmite
Chief Pilot Joined: 11 Apr 2008 Points: 1029 |
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Sure if you have unlimited memory in that sense then you would see an improvement since you wouldn't be writing to the slower hard drives, however you'd still run out of memory eventually |
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Marmite
Chief Pilot Joined: 11 Apr 2008 Points: 1029 |
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Which in turn affects physical memory.
http://support.microsoft.com/kb/555223 As I've said before, I'd rather leave paging turned on, at least it gives the OS something to fallback on if I run out of physical memory. |
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VulcanB2
Chief Pilot Joined: 02 Apr 2008 Points: 13365 |
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I know that in reality it is impossible, but when discussing the benefits of disabling the swap file, by assuming unlimited memory, and the fact that the system will swap memory out ANYWAY despite having lots of spare memory (unlimited in our example) then obviously it has performance BENEFITS. At the other extreme end of the scale is a system with 16 Mb of RAM running Windows XP. The system will be positively living out of the swap file, yes???? Best regards, Vulcan. |
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VulcanB2
Chief Pilot Joined: 02 Apr 2008 Points: 13365 |
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You see the word VIRTUAL? Do you need a dictionary?
Of course disabling the swap file will affected VIRTUAL memory. Sheesh. Virtual memory is but one small part of the overall scheme of memory management. You need to read the more general notes on memory management to understand this. Best regards, Vulcan. |
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Marmite
Chief Pilot Joined: 11 Apr 2008 Points: 1029 |
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That link just proves the point you argue against - "Components that make virtual memory work... A swap device" So therefore disabling a page file means there is no swap device, ergo screwing over the functionality of virtual memory since it has nowhere to store swapped pages. Edit: You posted while I was typing, memory cannot be "unlimited", you can probably theorise that but in the end it's a physical impossibility. The more memory you have the more computers will use that available memory |
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VulcanB2
Chief Pilot Joined: 02 Apr 2008 Points: 13365 |
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I don't see performance being cited as a reson to keep it. It just says not to disable it.
The reason not to disable is because if you have 128 Mb of RAM and tried to run FS, without a page file, FS would not even start as it would run out of memory. @Marmite: see why I said it was important to discuss the page file and performance from the point of view of UNLIMITED memory??? Best regards, Vulcan. |
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