On Thu, Aug 28, 2025 at 9:10 PM Andres Freund <and...@anarazel.de> wrote: > Same. Tomas, could you share what you applied?
Tomas posted a self-contained patch to the list about an hour ago? > > I'm not sure that Thomas'/your patch to ameliorate the problem on the > > read stream side is essential here. Perhaps Andres can just take a > > look at the test case + feature branch, without the extra patches. > > That way he'll be able to see whatever the immediate problem is, which > > might be all we need. > > It seems caused to a significant degree by waiting at low queue depths. If I > comment out the stream->distance-- in read_stream_start_pending_read() the > regression is reduced greatly. IIUC, that is very roughly equivalent to what the patch actually does. The fastest configuration of all, independent of io_method, is "enable_indexscan_prefetch=off". So it's hard to believe that the true underlying problem is low queue depth. Though I certainly don't doubt that higher queue depths will help *when io_method=worker*. -- Peter Geoghegan
