Thanks for the review! On Thu, May 21, 2026 at 2:38 PM vellaipandiyan sm <[email protected]> wrote: > > Hello hackers, > > I reviewed the EXPLAIN storage I/O patch and the overall direction seems > useful, especially for distinguishing shared-buffer hits from actual storage > reads during query analysis. > > One concern that stood out to me from the later discussion is the interaction > with asynchronous I/O and worker-based I/O accounting. > > Since the patch currently relies on per-process getrusage() statistics, it > seems possible that the reported values could become partial or misleading > once I/O is performed outside the backend process context. In particular, > worker-based AIO could undercount storage reads/writes while still returning > non-zero values, which may make the output appear more accurate than it > actually is.
Yeah, to avoid reporting the misleadingly underestimated values, no output is shown when worker-based AIO is used, as described in the docs: + ..Also, when + <xref linkend="guc-io-method"/> is set to <literal>worker</literal>, no output + will be shown, as I/O handled by asynchronous workers cannot be measured + accurately. > I also wonder whether this should affect the semantics/documentation of the > feature itself — i.e. whether the reported numbers should be described more > explicitly as “backend-observed synchronous storage I/O” rather than total > query I/O. Updated the patch to clarify that the reported values include not only the backend process executing the query, but also any parallel query worker processes involved in the query. -- Regards, Atsushi Torikoshi
v11-0001-Add-storage-I-O-tracking-to-BUFFERS-option.patch
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