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2008/8/12 Juan Fco. Giordana <juangiordana@×××××.com> |
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|
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> Morgan Wesström wrote: |
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> |
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>> If I follow this advice, what happens when I compile something like |
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>> Open Office which allocates 3-4GB in /var/tmp during compilation and |
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>> I only have 2GB physical RAM in the computer? |
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>> |
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> |
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> If all the Virtual Memory (VM = RAM+SWAP) is exhausted the kernel will try |
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> to kill the process that is consuming most of it. Daniel Robbins explains |
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> precisely that behaviour in this article: |
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> |
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> http://www.funtoo.org/en/articles/linux/ffg/3/ |
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> |
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> "So, the kernel mistakenly attacks the biggest VM-hog of a process it can |
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> find, which is generally your X server if you happen to be running one. So, |
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> your X server dies, and the root cause of the low-VM condition (tmpfs) isn't |
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> addressed. Ick." |
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> |
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> See "Avoiding low VM conditions". |
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> |
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> |
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if you're still using something the kernel won't kill nothing. the behaviour |
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you're referencing is the kernel cached pages. when you use something you |
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load it into memory. after you finish using it then the kernel will continue |
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to hold the pages in ram as cached pages, if you have enough space to be |
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able to speed up the eventual future reuse of that particular object. when |
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the ram is over certain quota the kernel will free some pages based on |
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different criteria like the oldness of the page or on how many times that |
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particular page has been used. for example if you use libdvdcss to decode a |
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dvd you'll have it in ram. let's assume that you then load another library |
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and use that library 30 times. then you'll reuse libdvdcss again and then |
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start a program that will consume quite some ram space, like openoffice. the |
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kernel will free the libdvdcss from ram and cache it into the swap partition |
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mantaining the other library into ram if possible, cause it has been used |
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more than once. this is a mere and very simple example of how the kernel |
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frees the ram space. |
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as for processes that are in use, from my knowledge, the kernel will not |
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kill anything unless the process doesn't reply to its interrupts. |
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|
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-- |
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dott. ing. beso |
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