Re: [PATCH 00/23] per device dirty throttling -v8

Brice Figureau
2007-08-14T07:59:58Z

On Tue, 2007-08-14 at 04:25 +0200, Andi Kleen wrote:
> On Tue, Aug 14, 2007 at 11:44:56AM +1000, Stewart Smith wrote:
> > > Since the database fits in RAM, the only kind of access Mysql is doing
> > > is writing to the innodb log, the mysql binlog and finally to the innodb
> > > database files.
> > > There are certainly a whole lot of fsync'ing happening.
> >
> > yes. Keep in mind that the binlog grows in file size too... so this has
> > to sync all the metadata as well (ick, i know).

Back in the first days of my original bug report I moved the binlogs to
another disk and it didn't change anything to my issue.

On Tue, 2007-08-14 at 04:25 +0200, Andi Kleen wrote:
> It might be an interesting experiment to see if it still happens
> with the file system remounted as ext2. ext2 has a much more
> benign fsync than ext3.

Is it possible to perform a live remount of the fs on ext2 ?

Beside that, the RAID card has a battery backed RAM in write-back mode,
I was told that fsync don't really hurt in this case (moreover the fs is
mounted in journal=writeback mode).

I'll post soon blktrace files in the original bug report, this will show
exactly what is the disk workload in the baseline case _and_ in the
underload atypical case. Maybe that will help to shed some lights on the
issue?

Anyway, thanks,
--
Brice Figureau <brice+lklm@daysofwonder.com>