Re: 2x Oracle slowdown from 2.2.16 to 2.4.4

[Chris Mason <mason@suse.com>]

On Thursday, July 12, 2001 12:14:16 PM +0200 Andi Kleen <freitag@alancoxonachip.com> wrote:

> Lance Larsh <llarsh@oracle.com> writes:
>> 
>> I ran lots of iozone tests which illustrated a huge difference in write
>> throughput between reiser and ext2.  Chris Mason sent me a patch which
>> improved the reiser case (removing an unnecessary commit), but it was
>> still noticeably slower than ext2.  Therefore I would recommend that
>> at this time reiser should not be used for Oracle database files.
> 
> When I read the 2.4.6 reiserfs code correctly reiserfs does not cause
> any transactions for reads/writes to allocated blocks; i.e. you're not extending
> the file, you're not filling holes and you're not updating atimes.
> My understanding is that this is normally true for Oracle, but probably
> not for iozone so it would be better if you benchmarked random writes
> to an already allocated file. 
> The 2.4 page cache is more or less direct write through in this case.
>

In general, yes.  But, atime updates trigger transactions, as
and O_SYNC/fsync writes (in 2.4.x reiserfs) always force a commit of
the current tranasction.  The two patches I just posted should fix
that...

-chris