Re: oom_killer - Mailing list pgsql-performance

2011/4/22 Tory M Blue <tmblue@gmail.com>:
> On Fri, Apr 22, 2011 at 4:03 AM, Cédric Villemain
> <cedric.villemain.debian@gmail.com> wrote:
>> 2011/4/21 Tory M Blue <tmblue@gmail.com>:
>>> On Thu, Apr 21, 2011 at 7:27 AM, Merlin Moncure <mmoncure@gmail.com> wrote:
>>>> On Thu, Apr 21, 2011 at 3:28 AM, Tory M Blue <tmblue@gmail.com> wrote:
>>>
>>>>> Fedora 12
>>>>> 32gig memory, 8 proc
>>>>> postgres 8.4.4, slony 1.20
>>>>> 5 gigs of swap (never hit it!)
>>>>
>>>> curious: using 32/64 bit postgres? what are your postgresql.conf
>>>> memory settings?
>>>>
>>>> merlin
>>>>
>>>
>>> 32bit
>>> 32gb
>>> PAE kernel
>>>
>>> # - Checkpoints -
>>> checkpoint_segments = 100
>>> max_connections = 300
>>> shared_buffers = 2500MB       # min 128kB or max_connections*16kB
>>> max_prepared_transactions = 0
>>> work_mem = 100MB
>>> maintenance_work_mem = 128MB
>>> fsync = on
>>>
>>
>> I didn't understand what value you set for vm.overcommit parameters.
>> Can you give it and the values in /proc/meminfo, the interesting one
>> are "Commit*" ?
>>
>> If you have strict rules(overcommit=2), then your current kernel
>> config may need some love : the commit_limit is probably too low
>> because you have a small swap partition. One way is to change :
>> vm.overcommit_ratio.
>> By default it should be something like 21GB (0.5*32+5) of
>> commit_limit, and you probably want 32GB :)
>>
>> Maybe you have some minor changes in your install or application usage
>> and you just hit the limit.
>
> Thanks Cedric
>
> the sysctl vm's are
>
> # 04/17/2011 to keep overcommit memory in check
> vm.overcommit_memory = 2
> vm.overcommit_ratio = 0
>
> CommitLimit:     4128760 kB
> Committed_AS:    2380408 kB

Are you sure it is a PAE kernel ? You look limited to 4GB.

I don't know atm if overcommit_ratio=0 has a special meaning, else I
would suggest to update it to something like 40% (the default), but
60% should still be safe (60% of 32GB + 5GB)

>
>
> Ya I do think my swap space is biting us, (but again just starting to
> grasp that my swap space which has not grown with the continued
> addition of memory). I am just not starting to learn that the swap
> does need to be properly sized whether it's being used or not. I
> figured it would use the swap and it would run out, but sounds like
> the system takes the size into consideration and just decides not to
> use it.
>
> I appreciate the totally no postgres responses with this.
>
> Thanks
> Tory
>



--
Cédric Villemain               2ndQuadrant
http://2ndQuadrant.fr/     PostgreSQL : Expertise, Formation et Support