On Wed, May 23, 2012 at 9:37 AM, Tom Lane <tgl@xxxxxxxxxxxxx> wrote: > Lonni J Friedman <netllama@xxxxxxxxx> writes: >> After banging my head on the wall for a long time, I happened to >> notice that khugepaged was consuming 100% CPU every time autovacuum >> was running. I did: >> echo "madvise" > /sys/kernel/mm/transparent_hugepage/defrag >> and immediately the entire problem went away. > > Fascinating. In hindsight, sure. Before that, it was 2 days of horror. > >> So this looks like a nasty Fedora16 kernel bug to me, or maybe >> postgresql & Fedora16's default kernel settings are just not >> compatible? > > I agree, kernel bug. What kernel version are you using exactly? I'm using the stock 3.3.5-2.fc16.x86_64 kernel that is in Fedora updates. > >> Is anyone else using Fedora16 & PostgreSQL-9.1 ? > > I use an F16 box daily, but can't claim to have done major performance > testing with it. Can you put together a summary of your nondefault > Postgres settings? I wonder whether it only kicks in for a certain > size of shared memory for instance. Oh yea, I'm quite certain that this is somehow related to my setup, and not a generic problem with all F16/pgsql systems. For starters, this problem isn't happening on any of the 3 standby systems, which are all otherwise identical to the master in every respect. Also when we had done some testing (prior to the upgrades), we never ran into any of these problems. However our test environment was on smaller scale hardware, with a much smaller number of clients (and overall load). Here are the non default settings in postgresql.conf : wal_level = hot_standby archive_mode = on archive_timeout = 61 max_wal_senders = 10 wal_keep_segments = 5000 hot_standby = on log_autovacuum_min_duration = 2500 autovacuum_max_workers = 4 maintenance_work_mem = 1GB checkpoint_completion_target = 0.7 effective_cache_size = 88GB work_mem = 576MB wal_buffers = 16MB checkpoint_segments = 64 shared_buffers = 8GB max_connections = 350 Let me know if you have any other questions. I'd be happy to provide as much information as possible if it can aid in fixing this bug. -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
