I'd like to do the PR, but could you please confirm to me that it's safe to use non-volatile field? I believe this should be the case.
Viliam On Thu, Jan 15, 2026 at 12:25 AM Michael Sokolov <[email protected]> wrote: > 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 > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [email protected] > For additional commands, e-mail: [email protected] > >
