Re: Load spikes on 8.1.11

Just an addition... the strace o/p with selects timing out just runs almost
continuously, it doesn't seem to pause anywhere!

On Fri, Jul 18, 2008 at 9:16 AM, Gurjeet Singh <singh(dot)gurjeet(at)gmail(dot)com>
wrote:

> Hi All,
>
> I have been perplexed by random load spikes on an 8.1.11 instance. many
> a times they are random, in the sense we cannot tie a particular scenario as
> the cause for it! But a few times we can see that when we are executing huge
> scripts, which include DDL as well as DML, the load on the box spikes to
> above 200. We see similar load spikes other times too when we are not
> running any such task on the DB.
>
> During these spikes, in the 'top' sessions we see the 'idle' PG
> processes consuming between 2 and 5 % CPU, and since the box has 8 CPUS (2
> sockets and each CPU is a quad core Intel Xeon processors) and somewhere
> around 200 Postgres processes, the load spikes to above 200; and it does
> this very sharply.
>
> We are running the scripts using psql -f, but we can see the load even
> while running the commands on by one!
>
> When there's no load, an strace session on an 'idle' PG process looks
> like:
>
> [postgres(at)db1 data]$ strace -p 9375
> Process 9375 attached - interrupt to quit
> recvfrom(9, <unfinished ...>
> Process 9375 detached
>
>
> But under these heavy load onditions, an 'idle' PG process' strace
> looks like:
>
> [postgres(at)db1 data]$ strace -p 22994
> Process 22994 attached - interrupt to quit
> select(0, NULL, NULL, NULL, {0, 1000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 10000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 11000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 14000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 17000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 31000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 51000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 1000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 1000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 1000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 2000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 4000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 5000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 1000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 2000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 2000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 3000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 6000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 12000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 12000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 23000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 27000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 47000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 70000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 1000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 1000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 2000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 4000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 7000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 11000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 16000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 19000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 35000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 53000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 75000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 76000}) = 0 (Timeout)
> select(0, NULL, NULL, NULL, {0, 102000}) = 0 (Timeout)
> Process 22994 detached
>
>
> So I guess there's something very wrong with the above 'select' calls.
>
> Can somebody please shed some light on this? Let me know what
> OS/hardware specs you need.
>
> Any help is greatly appreciated.
>
> Thanks in advance,
>
> --
> gurjeet[(dot)singh](at)EnterpriseDB(dot)com
> singh(dot)gurjeet(at){ gmail | hotmail | indiatimes | yahoo }.com
>
> EnterpriseDB http://www.enterprisedb.com
>
> Mail sent from my BlackLaptop device
>

--
gurjeet[(dot)singh](at)EnterpriseDB(dot)com
singh(dot)gurjeet(at){ gmail | hotmail | indiatimes | yahoo }.com

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