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[[!comment format=mdwn
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username="joey"
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subject="""comment 12"""
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date="2020-07-31T17:10:08Z"
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content="""
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It is premature optimisation to try to reduce these seeks when they have
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not been shown to reduce performance, and at least in my tests, have been
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shown to not affect it to the limits I can measure.
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I don't think it would be safe to consolidate all the libs into one
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directory, as I did in my test. Because it seems possible that there could
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be two versions of a .so file with the same name, in eg lib64/tls
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and lib64/x86_64. Installing only one of them would either lose actual
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optimisations in the other .so file, or cause breakage. I don't know when
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those optimised .so files exist, but implementating this consolidation
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would make the build more fragile.
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I don't know if `prelink(8)` is able to prelink things such that they can
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be relocated, as git-annex.linux can. I think it hardcodes a fixed path in
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the binary. Similarly, ld.so.cache (which is why this seeking doesn't
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happen on Debian AFAICS, not preliking) contains a list of directories and
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the libraries in them, so unless it were created by runshell the first
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time, it would not work. And creating it by runshell the first time would
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make the thing more complicated, and thus more fragile. (Also
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/sbin/ldconfig is 1mb in size so would increase the bundle rather a lot.)
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Also, I benchmarked prelinking back in
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[[!commit c4229be9a7a2318ef71b9ae433bc14bf604c9caf]] and the speedup was not
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measurable.
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So these are not appealing with the information I have. It's a very
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different situation than the ghc bug that was adding one directory
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to rpath for every haskell library, which had an easily measurable
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performance impact because there are hundreds of those libraries and 30000
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seeks did add up to a measurable time.
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"""]]
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