| From: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> |
|---|---|
| To: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: WALInsertLock tuning |
| Date: | 2011-06-07 07:27:27 |
| Message-ID: | 4DEDD2DF.5010002@enterprisedb.com |
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| Lists: | pgsql-hackers |
On 07.06.2011 10:21, Simon Riggs wrote:
> On Mon, Jun 6, 2011 at 11:25 PM, Robert Haas<robertmhaas(at)gmail(dot)com> wrote:
>> It strikes me, though, that we
>> could probably get nearly all of the benefit of this patch by being
>> willing to zero the first sizeof(XLogRecord) bytes following a record,
>> but not the rest of the buffer. That would pretty much wipe out any
>> chance of an xl_prev match, I think, and would likely still get nearly
>> all of the performance benefit.
>
> Which adds something onto the path of every XlogInsert(), rather than
> once per page, so I'm a little hesitant to agree.
You would only need to do it just before you write out the WAL. I guess
you'd need to grab WALInsertLock in XLogWrite() to prevent more WAL
records from being inserted on the page until you're done zeroing it,
though.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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