On Fri, 3 Dec 2021 at 06:27, Dilip Kumar <dilipbal...@gmail.com> wrote: > > On Tue, Nov 30, 2021 at 5:49 PM Simon Riggs > <simon.ri...@enterprisedb.com> wrote: > > > transam.c uses a single item cache to prevent thrashing from repeated > > lookups, which reduces problems with shared access to SLRUs. > > multitrans.c also has similar. > > > > I notice that subtrans. doesn't have this, but could easily do so. > > Patch attached, which seems separate to other attempts at tuning. > > Yeah, this definitely makes sense. > > > On review, I think it is also possible that we update subtrans ONLY if > > someone uses >PGPROC_MAX_CACHED_SUBXIDS. > > This would make subtrans much smaller and avoid one-entry-per-page > > which is a major source of cacheing. > > This would means some light changes in GetSnapshotData(). > > Let me know if that seems interesting also? > > Do you mean to say avoid setting the sub-transactions parent if the > number of sun-transactions is not crossing PGPROC_MAX_CACHED_SUBXIDS?
Yes. This patch shows where I'm going, with changes in GetSnapshotData() and XidInMVCCSnapshot() and XactLockTableWait(). Passes make check, but needs much more, so this is review-only at this stage to give a flavour of what is intended. (No where near replacing the subtrans module as I envisage as the final outcome, meaning we don't need ExtendSUBTRANS()). -- Simon Riggs http://www.EnterpriseDB.com/
rethink_subtrans.v4.patch
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