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Hi! |
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On Sun, Oct 21, 2012 at 08:02:47AM +0000, Duncan wrote: |
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> Bottom line, an empty @system set really does make a noticeable |
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> difference in parallel merge handling, speeding up especially --emptytree |
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> @world rebuilds but also any general update that has a significant number |
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> of otherwise @system packages and deps, dramatically. I'm happy. =:^) |
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I think "@system first" and "@system not merge in parallel" rules are safe |
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to break when you just doing "--emptytree @world" on already updated OS |
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because it's only rebuild existing packages, and all packages while |
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compiling will see same set of other packages (including same versions). |
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But when upgrading multiple packages (including some from original @system |
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and some from @world) this probably may result in bugs. |
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As for "--emptytree @world" speedup, can you provide benchmarked values? |
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I mean, only few packages forced to use only one CPU Core while compiling. |
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So, merging packages in parallel may save some time mostly for doing |
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unpack/prepare/configure/install/merge. All of them except configure |
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actually do a lot of I/O, which most likely lose a lot in speed instead of |
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gain when done in parallel (especially keeping in mind kernel bug 12309). |
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So, at a glance time you may win on configure you'll mostly lose on I/O, |
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and most of time all your CPU Cores will be loaded anyway while compiling, |
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and doing configure in parallel to compiling unlikely save some time. |
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This is why I think without actual benchmarking we can't be sure how |
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faster it became (if it became faster at all, which is questionable). |
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As for me, I found very effective way to speedup emerge is upgrading from |
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Core2Duo E6600 to i7-2600K overclocked to 4.6GHz. This speedup compilation |
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on my system in 6 times (kernel now compiles in just 1 minute). And to |
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speedup most other (non-compilation) portage operations I use 4GB tmpfs |
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mount on /var/tmp/portage/. |
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-- |
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WBR, Alex. |