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... |
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> To confuse you even more, there is a swappiness setting as well. On my old |
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> x86 rig, I have 2Gbs of ram. My hard drive is really slow since it is IDE. |
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> I set swappiness to 20. That tells the kernel that I have swap space but |
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> don't use it unless you must. For what I use the rig for, 2Gbs is plenty of |
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> ram. The lower the swappiness setting, the less the kernel will try to use |
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> ram. The higher the setting, the more it will try to use swap. |
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> |
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> I have a new rig that is amd64 and has SATA drives which are pretty fast. I |
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> still have swappiness set to 20. Why do I have it set to 20 when the drives |
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> are faster you ask? I have it set to 20 because I have 16Gbs of ram here. |
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> Even if I have portage's work directory on tmpfs and am compiling OOo, it |
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> should not need swap then either. |
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> |
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> By the way, my swap partition is 1Gb on both systems. Why have it this way |
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> since one machine has 2Gbs and one has 16Gbs? As it has been said, you want |
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> a little swap and even using a little swap is OK. You just don't want it to |
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> be using swap and actually swapping data all the time. On my old rig, it |
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> started out with 512Mbs. I use KDE and it got to the point where it was |
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> using enough ram that it was not just using swap and letting things sit, it |
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> was actively swapping data from swap and doing so a lot. It would only be |
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> using a 100Mbs sometimes 200Mbs. The point is, it was slowing the system |
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> down because of the swapping process. I bought a stick of ram and all was |
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> well again. It would still use a 100Mbs of swap at times but it would not |
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> be actively swapping the data back and forth so it wasn't a big deal. |
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> |
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> I think the point is this, it is good to have a little swap. It is even OK |
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> for it to use a little swap when it is mostly sitting there. When you |
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> notice it using swap and it is actively swapping and moving things back and |
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> forth, you need more memory. Having the swap may can save you from a crash |
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> but is can also give you a "time to add more ram" hint too. If Linux starts |
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> using swap a good bit, you need more ram. |
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OK, how can you determine when a machine is actively swapping and |
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moving things back and forth? Do you need to monitor the system with |
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a real-time tool during peak usage? |
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- Grant |
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