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Uwe Thiem <uwix@××××.na> wrote: |
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> There are too damn many myths about swap out there. Like this one: |
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> Always configure twice as much swap as you have ram. Why? |
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<OT> |
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Well, it depends on how swap is handled by system. In linux, your |
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total memory = physical memory + swap (as you wrote) |
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A couple years ago I got answer from HP, where they said with hp-ux: |
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total memory = physical memory + (swap - physical memory) |
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only if swap > physical memory ! |
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and |
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total memory = physical memory |
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if swap < physical memory |
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(in other words, it was completely useless to have swap < phys.memory, |
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and optimum was really swap = 2 * physical memory) |
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They explained to me, that hp-ux 11 (or at least that early version) |
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allocates part of swap of the same size as physical memory and mirrors |
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the whole image of ram into swap for performance reasons: when more |
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memory is needed, it can be immediatelly made free, because it is |
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already paged to disk. |
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So when I had 1GB RAM and 2GB swap, even right after system boot-up |
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only 1GB of swap were free (in the other half of swap there was already |
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mirror of physical memory), and I could not start any process which |
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needed more than 2GB total memory. |
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It seemed to me to be a complete vaste, and I was really angry, because |
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it was time when 4 GB disk was a luxury (and e.g. irix did not have |
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this strange "feature"). But things might have changed since then... |
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</OT> |
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Jarry |
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-- |
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Telefonieren Sie schon oder sparen Sie noch? |
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NEU: GMX Phone_Flat http://www.gmx.net/de/go/telefonie |
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-- |
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