[PATCH] D116367: [ELF][LTO] Call madvise(MADV_DONTNEED) on BitcodeFile buffers

Wed Dec 29 14:05:49 PST 2021

MaskRay added a comment.

In D116367#3212997 <https://reviews.llvm.org/D116367#3212997>, @tejohnson wrote:

> I tried a few times and didn't see a slowdown.
>
> However, with the latest version to only free the bitcode files, I am seeing less memory reduction (9.3G vs 9.1G before), and also a 30-40s slowdown (maybe the DenseSet lookups?). Something could probably be done to avoid the lookups, but do you have any idea why the memory reduction would be less? Hmm, probably there are some other non-bitcode files that are being read for symbol resolution but not being used further in index only mode?

It was my negligence. `--start-lib` bitcode files may not be extracted. They reside in the `lazyBitcodeFiles` list. The latest diff marked them as well.
I think this is sufficient for our use case. The diff tried a bit more to support other use cases.

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  https://reviews.llvm.org/D116367/new/

https://reviews.llvm.org/D116367