On 26 November 2017 at 08:46, Tom Lane <[email protected]> wrote: > I wrote: >> Instead I propose that we should make sure that the palloc request size >> for XLogReaderState->main_data is always maxalign'd. The existing >> behavior in DecodeXLogRecord of palloc'ing it only just barely big >> enough for the current record seems pretty brain-dead performance-wise >> even without this consideration. Generally, if we need to enlarge >> that buffer, we should enlarge it significantly, IMO. > > I've confirmed that the attached is sufficient to stop the valgrind crash > on my machine. But as I said, I think we should be more aggressive at > resizing the buffer, to reduce resize cycles. I'm inclined to start out > with a buffer size of 128 or 256 or so bytes and double it when needed. > Anybody have a feeling for a typical size for the "main data" part > of a WAL record?
We reuse the buffer and only pfree/palloc when we need to enlarge the buffer, so not sure we need to do the doubling thing and it probably doesn't matter what the typical size is. So I think we're just good to go with your patch. -- Simon Riggs http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
