Re: Block level parallel vacuum WIP

On Fri, Mar 3, 2017 at 11:01 PM, David Steele <david(at)pgmasters(dot)net> wrote:
> On 1/10/17 11:23 AM, Claudio Freire wrote:
>> On Tue, Jan 10, 2017 at 6:42 AM, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
>>>> Does this work negate the other work to allow VACUUM to use >
>>>> 1GB memory?
>>>
>>> Partly yes. Because memory space for dead TIDs needs to be allocated
>>> in DSM before vacuum worker launches, parallel lazy vacuum cannot use
>>> such a variable amount of memory as that work does. But in
>>> non-parallel lazy vacuum, that work would be effective. We might be
>>> able to do similar thing using DSA but I'm not sure that is better.
>>
>> I think it would work well with DSA as well.
>>
>> Just instead of having a single segment list, you'd have one per worker.
>>
>> Since workers work on disjoint tid sets, that shouldn't pose a problem.
>>
>> The segment list can be joined together later rather efficiently
>> (simple logical joining of the segment pointer arrays) for the index
>> scan phases.
>
> It's been a while since there was any movement on this patch and quite a
> few issues have been raised.
>
> Have you tried the approaches that Claudio suggested?
>

Yes, it's taking a time to update logic and measurement but it's
coming along. Also I'm working on changing deadlock detection. Will
post new patch and measurement result.

Regards,

--
Masahiko Sawada
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center