On Mon, 14 Jul 2003, Phil Barnett wrote: > On Monday 14 July 2003 8:03 am, Jonathan C. wrote: > > Hi all, > > > > A few months ago I talked with some people on this list about > > excessive caching on laptop computers. We could not find a > > solution. Howevber, the title of the thread was cryptic, so I hope > > that with the new title more people will react. > > > > We noticed that that copying a file or making extensive access to the > > hard drive ate up all the memory. For instance, when I copy a 200Mo > > file from one partition to another (same physical HD), the file copies > > fine but 200Mo of RAM get eaten up in the process. The question is : > > Is this gentoo related ? Is this kernel related ? Is this hardware > > related ? I may add that this seems to be vendor independent since > > both Dell and Toshiba laptops seem to have the same problem. > > Well, it's used, and it's available. > > Unused ram is wasted ram. Since Linux can't possibly know when you'll use a > disk read more than once, it uses all available spare ram to cache it. If you > need that ram for something else, it becomes instantly available (within > reason). > > This is a Linux design issue and is perfectly normal operation. > > Here's a ram snapshot from my server: > > 11:07am up 41 days, 20:42, 1 user, load average: 0.15, 0.24, 0.32 > Mem: 1023108K av, 1008392K used, 14716K free, 0K shrd, 71596K buff > Swap: 610384K av, 23352K used, 587032K free 778280K cached > > As you can see, Linux maintains a small amount of free ram (around 15 meg > here), and all other ram is used. In this case, 778M is just used as disk > cache, which means that over the long run, my server needs about 1/4th of the > ram that I have given it. However, this large disk cache means that many disk > reads come from ram instead of the hard drives. On a server, this is a great > thing. > > May I suggest that you run xosview and be concerned with the area in green.
Thank you for the explanation, I did not know how Linux managed its RAM, and thanks for the pointer to xosview, everything is clear now. Jonathan
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