maria-developers team mailing list archive

[Arjen Lentz <arjen@xxxxxxxxxxxxx>]

Hi Serg, Kristian, all

On 14/12/2010, at 4:08 PM, Sergei Golubchik wrote:
> On Dec 14, Arjen Lentz wrote:
> > Can we adopt/implement http://forge.mysql.com/worklog/task.php?id=4925 
> >  in
> > MariaDB?
> > The benchmark info is in the item, and looks quite interesting.
> > The author tested it using a separate tool to preallocate the  
> > binlog, but
> > it should be straightforward implementing this inside the server,  
> > that'd
> > also be much easier to manage without extra fuss for a DBA.
>
> You mean - before it gets into 5.6 and we merge it the normal way?
> Or you mean - with a different implementation (w/o mysqlbinlogalloc) ?


Both ;-)

sync_binlog=1 is a serious problem, note my earlier bugreport on the  
number of fsyncs a commit requires. While fixing that is not trivial,  
pre-allocating apparently makes a big difference. So I'd see that as  
high priority, even just looking in the realm of a number of Open  
Query clients.

Secondly, I think the implementation with the external  
mysqlbinlogalloc tool is not nice. I appreciate that writing full a  
1GB file takes a long time, but that's not how it needs to work.  
InnoDB can extend its tablespace with a configurable chunk at a time  
(8M by default, iirc).

The binlog_preallocate variable should, similar to the InnoDB method,  
define the size of the next preallocation. I also don't see the point  
of the =0 ignoring a preallocated file. Since mysqld always starts a  
new binlog on startup, it does not have to scan an existing file at  
that stage. For replication, surely it can detect what's going on  
without having a setting.
By having the pre-allocation size configurable, users can choose an  
amount that works best in their particular environment; with the right  
filesystem, it could be huge. Otherwise, more modest. Either way  
advantage can be gained.

Cheers,
Arjen.
--
Arjen Lentz, Exec.Director @ Open Query (http://openquery.com)
Remote expertise & maintenance for MySQL/MariaDB server environments.

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