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

From: Claudio Freire <klaussfreire(at)gmail(dot)com>
To: Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>
Cc: PostgreSQL-Dev <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [HACKERS] [PATCH] Vacuum: Update FSM more frequently
Date: 2018-03-02 13:50:28
Message-ID: CAGTBQpYCPwd0ApD+Jdt-mEJFxZxxjF34mkU-yjq796okLFszYw@mail.gmail.com
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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.

Attachment Content-Type Size
0001-Vacuum-Update-FSM-more-frequently-v8.patch text/x-patch 14.9 KB

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