On Wed, Mar 16, 2022 at 1:47 AM Nathan Bossart <nathandboss...@gmail.com> wrote: > > On Tue, Mar 15, 2022 at 11:04:26AM +0900, Michael Paquier wrote: > > On Mon, Mar 14, 2022 at 03:54:19PM +0530, Bharath Rupireddy wrote: > >> At times, the snapshot or mapping files can be large in number and one > >> some platforms it takes time for checkpoint to process all of them. > >> Having the stats about them in server logs can help us better analyze > >> why checkpoint took a long time and provide a better RCA. > > > > Do you have any numbers to share regarding that? Seeing information > > about 1k WAL segments being recycled and/or removed by a checkpoint > > where the operation takes dozens of seconds to complete because we can > > talk about hundred of gigs worth of files moved around. If we are > > talking about 100~200 files up to 10~20kB each for snapshot and > > mapping files, the information has less value, worth only a portion of > > one WAL segment. > > I don't have specific numbers to share, but as noted elsewhere [0], I > routinely see lengthy checkpoints that spend a lot of time in these cleanup > tasks. > > [0] https://postgr.es/m/18ED8B1F-7F5B-4ABF-848D-45916C938BC7%40amazon.com
I too don't have numbers in hand to share. But I have come across cases where checkpoints spend a good amount of time cleaning up/processing snapshots or mapping files. Regards, Bharath Rupireddy.