Hi, restoring a 1.5TB database with about 800k tables on i3.4xlarge AWS instace, PgSQL V12.15 on Ubuntu.
Running pg_restore with -j 16, I noticed the pg_restore is busy for an hour or so with IO at 80%+ and then most of processes start idling and only a few doing some work, disk IO at 1-2%, pg_stat_activity is mostly idle, same goes for CPU, and this state proceeds for further 6 hours, disk space increases very slowly. I thought because of a lot of small tables, number of workers should be increased to increase parallel efficiency, so I tried with -j 128. The situation was somewhat better, but most of the workers start idling, again disk IO lowers to about 4% util, CPU util goes to about 4%, too. Stracing workers produces the perpetual read call on most pg_restore workers: # strace -p 59567 strace: Process 59567 attached read(3, With only about 10 or so (out of 128) workers doing some actual work: strace -p 59367 -e sendto strace: Process 59367 attached sendto(4, "Q\0\0\0\263ALTER TABLE ONLY raw.space0"..., 180, MSG_NOSIGNAL, NULL, 0) = 180 sendto(4, "Q\0\0\0.TRUNCATE TABLE ONLY raw.spa"..., 47, MSG_NOSIGNAL, NULL, 0) = 47 sendto(4, "Q\0\0\0\205COPY raw.space000448117 (da"..., 134, MSG_NOSIGNAL, NULL, 0) = sendto(4, "Q\0\0\0\vCOMMIT\0", 12, MSG_NOSIGNAL, NULL, 0) = 12 sendto(4, "Q\0\0\0pCREATE INDEX idx_space00044"..., 113, MSG_NOSIGNAL, NULL, 0) = 113 sendto(4, "Q\0\0\0\263ALTER TABLE ONLY raw.space0"..., 180, MSG_NOSIGNAL, NULL, 0) = 180 ... .. some lines omitted I would think that all workers would proceed with creating indexes and doing some useful work until the restore is finished completely? Most of the tables are very small, 2 indexes per table and without any foreign references etc., we have a multi tenant environment. Thanks, Boris
