Re: [HACKERS] [PATCH] Vacuum: Update FSM more frequently

On Fri, Mar 2, 2018 at 10:47 AM, Claudio Freire <klaussfreire@gmail.com> wrote:
> On Fri, Mar 2, 2018 at 7:38 AM, Masahiko Sawada <sawada.mshk@gmail.com> wrote:
>> Thank you for updating the patches!
>>
>> +/*
>> + * When a table has no indexes, vacuum the FSM at most every this
>> + * many dirty pages. With a default page size of 8kb, this value
>> + * basically means 8GB of dirtied pages.
>> + */
>> +#define VACUUM_FSM_EVERY_PAGES 1048576
>>
>> Is it better if we vacuum fsm every 8GB regardless of the block size?
>> Because an installation that uses >8GB block size is likely to have
>> the pages less than what an 8GB block size installation has, the
>> current patch might lead to delay fsm vacuum. What do you think? If
>> it's better, we can define it as follows.
>>
>> #define VACUUM_FSM_EVERY_PAGES ((8 * 1024 * 1024) / BLCKSZ)
>
> I honestly don't know. I've never tweaked page size, and know nobody
> that did, so I have no experience with those installations.
>
> Lets go with your proposal.
>
>>
>> --
>> @@ -470,7 +484,9 @@ lazy_scan_heap(Relation onerel, int options,
>> LVRelStats *vacrelstats,
>>      TransactionId relfrozenxid = onerel->rd_rel->relfrozenxid;
>>      TransactionId relminmxid = onerel->rd_rel->relminmxid;
>>      BlockNumber empty_pages,
>> -                vacuumed_pages;
>> +                vacuumed_pages,
>> +                fsm_updated_pages,
>> +                vacuum_fsm_every_pages;
>>      double        num_tuples,
>>                  tups_vacuumed,
>>                  nkeep,
>>
>> Regarding fsm_updated_pages variable name, I think it's better to be
>> freespace_updated_pages because we actually counts the page updated
>> its freespace, not fsm.
>
> Good point.
>
> New version attached.

Sorry, forgot to actually squash. Now the real new version is attached.