From: Jason C. <ja...@ja...> - 2005-02-26 05:03:47
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I have recently seen an increase in traffic to one of my sites that is hosted using UML. Previously, I had allocated 128Megs of RAM and 1 gig of swap to each UML, but I never got close to touching the swap file. It always remained at 0% usage. With the traffic spike, I have noticed that I will drop all the way down to 200k of free RAM on a guest uml, but the swapfile is still never touched. I see it activated at boot, running `free` shows the swap file as being there, but the guest UML just doesn't want to use it. Can anyone shed some light on what makes my guest machines swap shy? Im running 2.6.10 skas3v7 as the host and 2.6.9bs6 guests. |
From: Paul W. <pd...@ex...> - 2005-02-27 21:48:20
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On Fri, Feb 25, 2005 at 05:06:46PM -0600, Jason Clark wrote: > I have recently seen an increase in traffic to one of my sites that is > hosted using UML. Previously, I had allocated 128Megs of RAM and 1 gig of > swap to each UML, but I never got close to touching the swap file. It > always remained at 0% usage. With the traffic spike, I have noticed > that I will drop all the way down to 200k of free RAM on a guest uml, > but the swapfile is still never touched. When you say 200k of free RAM, which figure are you reading? It is normal for Linux to use up all available RAM under normal usage, as it will retain a cache of disk pages. It will throw these away if there is a real need for the RAM. For this reason, free will claim close to 100% memory usage long before it actually hits swap. Paul |
From: Jason C. <ja...@ja...> - 2005-02-28 05:02:11
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I'll hammer it a bit harder and see if I can get it to release those last few pages into swap. Thanks. On Sun, 27 Feb 2005, Paul Warren wrote: > On Fri, Feb 25, 2005 at 05:06:46PM -0600, Jason Clark wrote: >> I have recently seen an increase in traffic to one of my sites that is >> hosted using UML. Previously, I had allocated 128Megs of RAM and 1 gig of >> swap to each UML, but I never got close to touching the swap file. It >> always remained at 0% usage. With the traffic spike, I have noticed >> that I will drop all the way down to 200k of free RAM on a guest uml, >> but the swapfile is still never touched. > > When you say 200k of free RAM, which figure are you reading? It is > normal for Linux to use up all available RAM under normal usage, as it > will retain a cache of disk pages. It will throw these away if there is > a real need for the RAM. For this reason, free will claim close to 100% > memory usage long before it actually hits swap. > > Paul > |
From: Paul W. <pd...@ex...> - 2005-02-28 09:41:11
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On Sun, Feb 27, 2005 at 05:05:35PM -0600, Jason Clark wrote: > I'll hammer it a bit harder and see if I can get it to release those last > few pages into swap. Thanks. Well, if you're trying to prove that it will actually swap, then a simple C program of the form: int main(int argc, char** argv) { calloc(100,1024*1024); sleep(100); return 0; } Will attempt to allocate 100MB of RAM. The second line of output from "free" will give you a much better indication of how much RAM is available before it will start swapping. Paul > On Sun, 27 Feb 2005, Paul Warren wrote: > > > On Fri, Feb 25, 2005 at 05:06:46PM -0600, Jason Clark wrote: > >> I have recently seen an increase in traffic to one of my sites that is > >> hosted using UML. Previously, I had allocated 128Megs of RAM and 1 gig of > >> swap to each UML, but I never got close to touching the swap file. It > >> always remained at 0% usage. With the traffic spike, I have noticed > >> that I will drop all the way down to 200k of free RAM on a guest uml, > >> but the swapfile is still never touched. > > > > When you say 200k of free RAM, which figure are you reading? It is > > normal for Linux to use up all available RAM under normal usage, as it > > will retain a cache of disk pages. It will throw these away if there is > > a real need for the RAM. For this reason, free will claim close to 100% > > memory usage long before it actually hits swap. > > > > Paul > > > > > ------------------------------------------------------- > SF email is sponsored by - The IT Product Guide > Read honest & candid reviews on hundreds of IT Products from real users. > Discover which products truly live up to the hype. Start reading now. > http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click > _______________________________________________ > User-mode-linux-user mailing list > Use...@li... > https://lists.sourceforge.net/lists/listinfo/user-mode-linux-user |
From: Jason C. <ja...@ja...> - 2005-02-28 12:25:47
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Thank you very much Paul, I guess I just wasn't hitting my machines as hard as I thought. Swap did it's job and paged out. Thanks again! On Mon, 28 Feb 2005, Paul Warren wrote: > On Sun, Feb 27, 2005 at 05:05:35PM -0600, Jason Clark wrote: >> I'll hammer it a bit harder and see if I can get it to release those last >> few pages into swap. Thanks. > > Well, if you're trying to prove that it will actually swap, then a > simple C program of the form: > > int main(int argc, char** argv) { > calloc(100,1024*1024); > sleep(100); > return 0; > } > > Will attempt to allocate 100MB of RAM. > > The second line of output from "free" will give you a much better > indication of how much RAM is available before it will start swapping. > > Paul > >> On Sun, 27 Feb 2005, Paul Warren wrote: >> >>> On Fri, Feb 25, 2005 at 05:06:46PM -0600, Jason Clark wrote: >>>> I have recently seen an increase in traffic to one of my sites that is >>>> hosted using UML. Previously, I had allocated 128Megs of RAM and 1 gig of >>>> swap to each UML, but I never got close to touching the swap file. It >>>> always remained at 0% usage. With the traffic spike, I have noticed >>>> that I will drop all the way down to 200k of free RAM on a guest uml, >>>> but the swapfile is still never touched. >>> >>> When you say 200k of free RAM, which figure are you reading? It is >>> normal for Linux to use up all available RAM under normal usage, as it >>> will retain a cache of disk pages. It will throw these away if there is >>> a real need for the RAM. For this reason, free will claim close to 100% >>> memory usage long before it actually hits swap. >>> >>> Paul >>> >> >> >> ------------------------------------------------------- >> SF email is sponsored by - The IT Product Guide >> Read honest & candid reviews on hundreds of IT Products from real users. >> Discover which products truly live up to the hype. Start reading now. >> http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click >> _______________________________________________ >> User-mode-linux-user mailing list >> Use...@li... >> https://lists.sourceforge.net/lists/listinfo/user-mode-linux-user > |