Re: Apparent deadlock for simultaneous sequential scans
От | Tom Lane |
---|---|
Тема | Re: Apparent deadlock for simultaneous sequential scans |
Дата | |
Msg-id | 12114.992037098@sss.pgh.pa.us обсуждение исходный текст |
Ответ на | Re: Apparent deadlock for simultaneous sequential scans (bruc@stone.congenomics.com (Robert E. Bruccoleri)) |
Список | pgsql-bugs |
bruc@stone.congenomics.com (Robert E. Bruccoleri) writes: > With two processors running the same query, it appears to be a > slowdown. When I look at the system calls, the backends were > executing about one read per second. With six processors running the > same query, it appeared to be a deadlock -- no I/O's were being issued > over the time that I watched. It's hard to believe there's an actual deadlock here. You might be looking at pathological inefficiency of the spinlock implementation, but still it seems that someone somewhere must be getting some work done. Can you determine which backend actually has the spinlock? What's it doing? Given that you mentioned you had a large number of shared buffers, it might be that a background checkpoint process running BufferSync() is part of the problem. It looks like BufferSync acquires the spinlock separately for each buffer it examines, which would be kinda nasty in the presence of heavy contention. OTOH we shouldn't really care if BufferSync is slow. regards, tom lane
В списке pgsql-bugs по дате отправления: