Originally posted by Pseus
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Torvalds Is Unconvinced By LTO'ing A Linux Kernel
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Originally posted by Brane215 View PostI....
I've toyed with it and have seen many weird errors, so I recompiled everything with bog standard "-march=native -O2"
LTO is interesting as an idea, but with this gcc and binutils... no, thanks. I'll wait for next round of gcc before I try again.
LTO seems much safer, though any gain for desktop users is doubtful due to the fact that distribution kernels are super robust and have everything in modules, which is presumably least effective use-case for LTO (and yet, most widely used).
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Liska's thesis was linked in the thread. So soon LTO will allow the compiler to de-duplicate functions. They're also adding it to the linker, as each can catch different parts.
That saves 5% off Firefox binary size, because C++ generated a few thousand variants of a "increase reference count" function. Each with a different type of pointer, yet compiled to the exact same instructions.
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Originally posted by curaga View PostLiska's thesis was linked in the thread. So soon LTO will allow the compiler to de-duplicate functions. They're also adding it to the linker, as each can catch different parts.
That saves 5% off Firefox binary size, because C++ generated a few thousand variants of a "increase reference count" function. Each with a different type of pointer, yet compiled to the exact same instructions.
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Smaller size benefits all, not just embedded.
Originally posted by caligula View PostI understand that 5% off is important in 4 MB flash storage. However in desktop apps it doesn't matter at all. Hard drives are now 1 TB (ssd) and 4 TB (3.5" hdd). You can also set up raid6 or zfs. So you get tens of terabytes and it's very cheap. You shouldn't bother with binary sizes. In fact there's plenty of room for more functionality in Firefox. Luckily they're working hard at implementing more new features with each release.
While stability is a major concern as Linus points out, smaller size generally benefits everything.
Loading times, memory contention, cache usage etc.
Just reducing size while maintaining everything else will generate a speedup.
If it is measurable in comparison to general code behavior or not, that is another question.
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Originally posted by milkylainen View PostSaying that 5% size does not matter on desktop is a misunderstanding on how computers work.
While stability is a major concern as Linus points out, smaller size generally benefits everything.
Loading times, memory contention, cache usage etc.
Just reducing size while maintaining everything else will generate a speedup.
If it is measurable in comparison to general code behavior or not, that is another question.
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