On Tue, Apr 28, 2026 at 9:38 AM shveta malik <[email protected]> wrote: > > On Mon, Apr 27, 2026 at 10:32 PM SATYANARAYANA NARLAPURAM > <[email protected]> wrote: > > > > Hi, > > > > On Mon, Apr 27, 2026 at 2:48 AM shveta malik <[email protected]> wrote: > >> > >> On Mon, Apr 27, 2026 at 2:11 PM SATYANARAYANA NARLAPURAM > >> <[email protected]> wrote: > >> > > >> > Hi Hackers, > >> > > >> > When a subscription has retain_dead_tuples enabled with maxretention set > >> > to zero (unlimited retention), adjust_xid_advance_interval() caps > >> > xid_advance_interval to Min(interval, maxretention). Since maxretention > >> > is zero, this always collapses the interval to zero milliseconds. > >> > > >> > A zero makes TimestampDifferenceExceeds(last_time, now, 0) always > >> > true in get_candidate_xid(). This causes the apply worker to call > >> > GetOldestActiveTransactionId() on every single WAL message. This results > >> > in > >> > a huge number of ProcArrayLock acquisitions under moderate write load. > >> > > >> > Fix by adding a maxretention > 0 guard to the cap. When maxretention is > >> > zero , > >> > the exponential back-off in adjust_xid_advance_interval() > >> > now works correctly, growing the interval from 100 ms toward the 180 s > >> > ceiling. > >> > > >> > Measured with perf uprobe counting GetOldestActiveTransactionId calls > >> > at ~39K TPS (pgbench, 5 clients): > >> > > >> > Before fix: 25,104 calls / 5 s (~5,021/s) > >> > After fix: 31 calls / 5 s (~6/s) > >> > > >> > >> Thanks for reporting it. I am reveiwing the problem sattement. > >> Meanwhile can you please look at it, I am getting the following error > >> while applying the patch on my Ubuntu setup (git am): > >> > >> error: corrupt patch at line 22 > > > > > > Thanks! Please find the updated v2 patch. > > Thanks. The patch looks good. >
LGTM as well, so pushed. -- With Regards, Amit Kapila.
