Re: Why not try for a HOT update, even when PageIsFull()?
On Sun, Nov 21, 2021 at 4:29 PM Peter Geoghegan wrote: > On Fri, Nov 19, 2021 at 11:51 AM Alvaro Herrera > wrote: > > I certainly do not object to removing it. > > I'd like to do so soon. I'll wait a few more days, in case Pavan objects. Pushed just now. Thanks -- Peter Geoghegan
Re: Why not try for a HOT update, even when PageIsFull()?
On Fri, Nov 19, 2021 at 11:51 AM Alvaro Herrera wrote: > Hmm, I don't have any memory of introducing this; and if you look at the > thread, you'll notice that it got there between the first patch I posted > and the second one, without any mention of the reason. I probably got > that code from the WARM patch series at some point, thinking that it was > an obvious optimization; but I'm fairly certain that we didn't run any > tailored micro-benchmark to justify it. I suspected that it was something like that. I agree that it's unlikely that we'll be able to do another HOT update for as long as the page has PD_PAGE_FULL set. But that's not saying much; it's also unlikely that heap_update will find that PD_PAGE_FULL is set to begin with. And, the chances of successfully applying HOT again are workload dependent. > I certainly do not object to removing it. I'd like to do so soon. I'll wait a few more days, in case Pavan objects. Thanks -- Peter Geoghegan
Re: Why not try for a HOT update, even when PageIsFull()?
On 2021-Nov-17, Peter Geoghegan wrote: > Commit 2fd8685e7f simplified the checking of modified attributes that > takes place within heap_update(). This included a micro-optimization > that affects pages marked PageIsFull(): when the target page is marked > with PD_PAGE_FULL (which must have been set by a previous heap_update > call), don't even try to use HOT -- assume that we have no chance in > order to save a few cycles on determining HOT safety. Hmm, I don't have any memory of introducing this; and if you look at the thread, you'll notice that it got there between the first patch I posted and the second one, without any mention of the reason. I probably got that code from the WARM patch series at some point, thinking that it was an obvious optimization; but I'm fairly certain that we didn't run any tailored micro-benchmark to justify it. Pavan may have something to say about it, so I CC him. I certainly do not object to removing it. -- Álvaro Herrera 39°49'30"S 73°17'W — https://www.EnterpriseDB.com/ "Find a bug in a program, and fix it, and the program will work today. Show the program how to find and fix a bug, and the program will work forever" (Oliver Silfridge)
