[PATCH] D64306: [clangd] Use xxhash instead of SHA1 for background index file digests.

[Sam McCall via Phabricator via llvm-commits]

sammccall added a comment.

In D64306#1572961 <https://reviews.llvm.org/D64306#1572961>, @kadircet wrote:

> LGTM.
>
> Out of curiosity what was the use case yielded the profile? I hope it is a use case with a lot of loading from disk storage, and only a few indexing operations?
>  Because in that case we're mostly IO bound, but if it is the other way around and this pops up as a 10% percent cpu usage, while we're performing (CPU bound) indexing part, it definitely sounds scary and something else might be wrong.


(As discussed offline, nothing new here)
Load is starting clangd on an index of the LLVM project itself. This is 100M of shards on disk, around 7 sec of CPU loading shards, and 8 sec of CPU building Dex structures. (On my machine, without any of my perf patches, measured using gperftools cpu profiler). That CPU usage is single-threaded. I don't think we're actually IO-bound.


Repository:
  rL LLVM

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D64306/new/

https://reviews.llvm.org/D64306