Re: WIP: Fast GiST index build

On 30.08.2011 13:29, Alexander Korotkov wrote:
> On Tue, Aug 30, 2011 at 1:13 PM, Heikki Linnakangas<
> heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
>
>> So, over 50% of the CPU time is spent in choosing a block from the
>> temporary files. That should be pretty easy to improve..
>>
> Yes, probably we can just remove free blocks sorting.

Ok, the first results are in for that:

testname | nrows | duration | accesses
---------------------------+-----------+-----------------+----------
points unordered buffered | 250000000 | 06:00:23.707579 | 4049832

From the previous test runs, the unbuffered index build took under 4
hours, so even though this is a lot better than with the sorting, it's
still a loss compared to non-buffered build.

I had vmstat running during most of this index build. At a quick glance,
it doesn't seem to be CPU bound anymore. I suspect the buffers in the
temporary file gets very fragmented. Or, we're reading it in backwards
order because the buffers work in a LIFO fashion. The system seems to be
doing about 5 MB/s of I/O during the build, which sounds like a figure
you'd get for more or less random I/O.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com