On Wed, Sep 10, 2014 at 2:25 PM, Heikki Linnakangas
<hlinnakangas@vmware.com> wrote:
> The dense-alloc-v5.patch looks good to me. I have committed that with minor
> cleanup (more comments below). I have not looked at the second patch.
Gah. I was in the middle of doing this. Sigh.
>> * the chunks size is 32kB (instead of 16kB), and we're using 1/4
>> threshold for 'oversized' items
>>
>> We need the threshold to be >=8kB, to trigger the special case
>> within AllocSet. The 1/4 rule is consistent with ALLOC_CHUNK_FRACTION.
>
> Should we care about the fact that if there are only a few tuples, we will
> nevertheless waste 32kB of memory for the chunk? I guess not, but I thought
> I'd mention it. The smallest allowed value for work_mem is 64kB.
I think we should change the threshold here to 1/8th. The worst case
memory wastage as-is ~32k/5 > 6k.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
