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On 20/10/19 10:59, Mick wrote: |
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> On Sunday, 20 October 2019 00:35:56 BST Wol's lists wrote: |
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> |
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>> The original swap algorithm NEEDED twice ram as swap. And when Linus |
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>> ripped out all the "optimisation", the vanilla kernels only needed to |
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>> touch swap, and if they didn't have twice ram they would crash. |
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> |
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> Was this also the time when the default swappiness was set at 60? |
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> |
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> |
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>> At that point, the recommendation changed to "no swap is fine, twice or |
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>> more is fine, just don't have swap less than twice ram". |
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> |
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> Are you sure of this? At least on current kernels (I'm currently on 4.19.72- |
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> gentoo) the overcommit_accounting kernel mechanism using a heuristic over- |
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> commit memory handling is set at 0, which refuses wilder over commits, but |
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> allows more measured over commits to use swap space. |
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> |
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> |
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> From the above and without further experimentation I assume having a swap |
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> slightly larger than my RAM is more than adequate for a desktop, including |
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> hibernating on swap. |
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> |
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As per Richard Brown, the current recommendation seems to be even less |
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than that ... "2GB is plenty". That's the SUSE default. |
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> |
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>> My personal rule is to take the motherboard's max ram, double it, and |
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>> create a swap partition that size on every disk. So my current desktop |
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>> system has 80GB of ram/swap - 4x4GB slots times 2 disk drives. And my |
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>> new system has 4x8GB so that'll be 160GB!!! HOWEVER - Richard Brown of |
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>> SUSE said that's dangerous - if somebody fork-bombs you it'll take a |
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>> long time to fill that much swap and regaining control of your system |
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>> could well be a big red switch job. |
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>> |
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> |
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> Each to their own, but I tend to think this huge amount of swap is probably |
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> excessive, unless you're running some scientific applications which require |
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> big over commits for their calculations. |
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> |
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Well, I do all my emerges on tmpfs, so if things like LO, firefox et al |
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need maybe 10GB, I need at least that available ... (that said, 16GB ram |
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could probably do it without needing swap :-) |
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But seeing as I try to fill up my mobo ram, my disks are mirrored, and I |
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still try and stick to the "twice ram" rule, this setup means any |
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upgrades/changes to the computer means I don't break that rule. If it's |
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overkill, well disk is cheap (and I can always nick a swap partition and |
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repurpose it temporarily if needs be :-) |
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Cheers, |
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Wol |
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