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

On Fri, Mar 2, 2018 at 10:50 PM, Claudio Freire <klaussfreire(at)gmail(dot)com> wrote:
> On Fri, Mar 2, 2018 at 10:47 AM, Claudio Freire <klaussfreire(at)gmail(dot)com> wrote:
>> On Fri, Mar 2, 2018 at 7:38 AM, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)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.

Thank you for updating. I think the patches has enough discussion and
quality, so can go to the committer's review. I've marked them as
Ready for Committer.

Regards,

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