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On Freitag, 3. August 2007, Richard Freeman wrote: |
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> Volker Armin Hemmann wrote: |
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> > emm, from my very personal point of view: no |
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> > |
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> > swap is horrible slow. Its use must be avoided at any cost. Swap sucks. |
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> > Everything is faster than accessing swap. So hitting the disk to read or |
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> > write some files is IMHO better than hitting the disk to shove X into |
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> > swap. |
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> > |
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> > X in swap is another problem. You can be sure, if X is forced into swap, |
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> > because gcc uses up all ram for itself, everything sucks. Mouse is jerky, |
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> > windows need ages to get displayed. |
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> |
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> Depends - if you're not using X then you won't mind X getting swapped |
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> (running emerge from ssh/etc). If you are using X then chance are it |
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> won't get swapped in the first place. If the issue is gcc using all ram |
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> for itself, then the presence/absence of tmpfs probably won't make much |
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> difference - gcc still has to run. |
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> |
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> I don't see why swap should be any better/worse than any other form of |
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> disk access. If anything it is superior as it allows the kernel to |
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> manage it like any other form of RAM, and the kernel isn't forced to |
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> flush it out to disk within some time (writes to a filesystem are forced |
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> to sync within some time to prevent data loss - this hurts performance |
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> and is totally unnecessary for temporary build files that will get |
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> deleted when you re-run emerge anyway). |
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where is the difference between 'app syncs its files to disk' and 'kernel |
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swaps app to disk, than decides to swap it in, so app can decides which files |
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it wants to sync to disk, then swap it out again'? |
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oh, more disk access... |
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> |
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> Now, if somebody has empirical data I'll certainly pay attention, or at |
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> least a lot of expertise. However, I wouldn't jump to the conclusion |
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> that swap is worse than ordinary disk writes - linux manages swap fairly |
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> well all things considered. If you don't like how it is being managed |
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> there are kernel settings that can be used to tweak it (swappiness, etc). |
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swappiness just prevents the kernel from swapping, when their is enough ram |
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left. It does not improve the speed of swap. |
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And honestly? From my 'feelings' swap is way slower than normal disk accesses. |
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-- |
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