On Tue, Feb 6, 2024 at 4:23 PM Alvaro Herrera <alvhe...@alvh.no-ip.org> wrote: > > > > (We also have SimpleLruTruncate, but I think it's not as critical to > > > have a barrier there anyhow: accessing a slightly outdated page number > > > could only be a problem if a bug elsewhere causes us to try to truncate > > > in the current page. I think we only have this code there because we > > > did have such bugs in the past, but IIUC this shouldn't happen anymore.) > > > > +1, I agree with this theory in general. But the below comment in > > SimpleLruTrucate in your v3 patch doesn't seem correct, because here > > we are checking if the latest_page_number is smaller than the cutoff > > if so we log it as wraparound and skip the whole thing and that is > > fine even if we are reading with atomic variable and slightly outdated > > value should not be a problem but the comment claim that this safe > > because we have the same bank lock as SimpleLruZeroPage(), but that's > > not true here we will be acquiring different bank locks one by one > > based on which slotno we are checking. Am I missing something? > > I think you're correct. I reworded this comment, so now it says this: > > /* > * An important safety check: the current endpoint page must not be > * eligible for removal. This check is just a backstop against wraparound > * bugs elsewhere in SLRU handling, so we don't care if we read a slightly > * outdated value; therefore we don't add a memory barrier. > */ > > Pushed with those changes. Thank you!
Yeah, this looks perfect, thanks. > Now I'll go rebase the rest of the patch on top. Okay, I will review and test after that. -- Regards, Dilip Kumar EnterpriseDB: http://www.enterprisedb.com
