yeah this looks silly: do you want to open a PR to fix? On Mon, Jan 12, 2026 at 6:39 AM Viliam Ďurina <[email protected]> wrote: > > Hi all, > > I'm looking at `OnHeapHnswGraph` code and noticed that the volatile field > `graphRamBytesUsed` is modified in `addNode` in a racy way: > > long bytesUsed = graphRamBytesUsed; > graphRamBytesUsed = bytesUsed + l; > > This is equivalent to `graphRamBytesUsed += l`. > > This code is susceptible to lost update due to non-atomic read-modify-write > operation. > > I guess the it's not really a problem, because this code is in fact > single-threaded when documents are added to the index. It might be > concurrent during merging, but then `ramBytesUsed()` isn't called, and it's > a wasted work. > > If the above assumption is correct, then this field should not be volatile > to improve performance. If it's not, it should be replaced with > `AtomicLong` or `LongAdder`. > > Viliam
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