Huge pagefile

In the recent past I had to overcome unexplained OS size fluctuations. Then yesterday I got one of those dreaded popups saying I was low on space.

I discovered that I had a 16 gb pagefile. Never seen anything like this.

My OS partition is 40 gb (on a ssd), with 16 gb ram, and if things are right, I have about 20 gb free space.

My only theory is that I had download several 2 gb files yesterday, which took longer than expected. I have windows managing the page file, so maybe that's why the pagefile grew??

I deleted the pagefile, and got the space back, but when I tried to reinstate the windows management, it immediately recreated the 16 gb pagefile.

I would prefer having windows manage the pagefile,and I don't think it would be wise turn turn it of, from what I understand. I just wanna get it back to where it was before.

Hi there
rule of thumb is that page file size should be equal to the amount of RAM in system

Note Windows doesn't have a conventional swapping file - both are managed in the paging file so it needs to have a proper size.

Paging simply moves the relevant memory address(es) from Disk back to RAM -- it may have been moved because the area required hasn't been active -- system running a different program for example.

Swapping is when a whole program area is backed off to HDD -- this occurs mainly if you are trying to run too many concurrent applications on a RAM constrained system. Overcommitting the paging file (i.e overallocating its size) won't cause any problems --you know when you have a problem on your system is when you see HDD light almost solid on for most of the time and response is very poor.

Modern OS'es are designed to run with Page / SWAP (Demand paging) so running with none is not a good idea -- the system will create a temporary (non persistent) one by default at every boot up and your boot will therefore take longer. What's even worse is that if there isn't sufficient HDD space it will create this in RAM reducing the amount of RAM even further so unless you have a system with something like 64 GB or 128 GB RAM then always ensure page file is allocated (and to the fasted device).

Those interested in a bit of theory (quite high level maths needed) can read about demand paging OS'es and the optimum page size works out at approx the RAM size.

Having smaller paging files can work on an SSD but the performance of the OS will still be diminished -- SSD's are cheap enough these days -- no point running the OS on "Starvation space". !!

Cheers
jimbo

CountMike said:

Page file can only slow down systems with enough RAM even on an SSD although not as much as on HDD but whatever pagefile size is, it doesn't mean it would be all used. If space is at premium, one can only make PF smaller and see what happens.

Hi there

?????

Normally you are 100% correct but have you understood what DEMAND paging is -- emphasis on word DEMAND.

Hate to be negative here but this topic is quite complex and there's a huge lot of B/S written about this topic.

There's no way in 10 zillion years why an OS with properly written paging algorithms would slow down because it had a paging file rather than didn't unless the entire OS ran entirely from a RAM Disk which Windows doesn't currently do (although in principle there's no reason why it shouldn't - so long as changes are logged to HDD / SSD and written away before OS shuts down).

There's too many people here who either have never written parts of an OS which uses demand paging -- I can remember one of the very first OS'es to use this concept : -- IBM mainframe's MVS in the 1970's - still even today a model for OS'es -- or don't understand how the system works. I remember working on all sorts of things such as Task control, switching, privileged state, supervisor calls, back to application state. Main development was in an internal language called PL/S (a bit like PL/I but this then created IBM machine code - the early versions translated it into IBM Assembler language which were run through the system Assembler to create machine code and executable programs but later PL/S did that in one step.

Remember also that decent OS'es overlap I/O with CPU processing so while the CPU is doing other things the I/O sub system (HDD / SSD controller etc) would be doing "pre-fetching" /organising page management without interrupting the CPU process bound tasks -- all good for the user and system response.

Cheers
jimbo

I can recall where the written recommendation in Windows Help and Support for the Virtual Memory/paging file/swap file was for 2.5 times the physical RAM installed and I believe Win7 had that dropped to 1.5 times. The only real reason I ever found for manually setting the Virtual Memory to the same Maximum and Minimum size was to prevent fragmentation, kept all the clusters adjacent to the others which with slower HDDs could and did improve performance especially with video editing, large spreadsheets and databases. Defragmentation helps the Read/Write search function in locating data. The advent of the SSDs eliminated that electromechanical issue.

kitpzyxmsir said:

In the recent past I had to overcome unexplained OS size fluctuations. Then yesterday I got one of those dreaded popups saying I was low on space.

I discovered that I had a 16 gb pagefile. Never seen anything like this.

My OS partition is 40 gb (on a ssd), with 16 gb ram, and if things are right, I have about 20 gb free space.

My only theory is that I had download several 2 gb files yesterday, which took longer than expected. I have windows managing the page file, so maybe that's why the pagefile grew??

I deleted the pagefile, and got the space back, but when I tried to reinstate the windows management, it immediately recreated the 16 gb pagefile.

I would prefer having windows manage the pagefile,and I don't think it would be wise turn turn it of, from what I understand. I just wanna get it back to where it was before.

You can't just delete the page file, you would go to system/advanced system properties/performance settings/ advanced tab Virtual Memory there you can uncheck the "Automatically manage Page file size" then you can set the size you want, maybe the 1 GB as suggested by using Max 1gb min 1gb or select no page file at all. As stated earler you don't really need a page file with a SSD.