Re: WALInsertLock tuning

On Tue, Jun 7, 2011 at 8:27 AM, Heikki Linnakangas
<heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
> 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.

How would that help?

--
 Simon Riggs                   http://www.2ndQuadrant.com/
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