linux-kernel - Re: [RFC] ext3: per-process soft-syncing data=ordered mode

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Date:	Mon, 28 Jan 2008 23:17:19 +0300
From:	Al Boldi <a1426z@...ab.com>
To:	Jan Kara <jack@...e.cz>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC] ext3: per-process soft-syncing data=ordered mode

Jan Kara wrote:
> On Sat 26-01-08 08:27:59, Al Boldi wrote:
> > Do you mean there is a locking problem?
>
>   No, but if you write to an mmaped file, then we can find out only later
> we have dirty data in pages and we call writepage() on behalf of e.g.
> pdflush().

Ok, that's a special case, which we could code for, but doesn't seem 
worthwile.  In any case, child-forks should inherit its parent mode.

> > > And in case of DB, they use direct-io
> > > anyway most of the time so they don't care about journaling mode
> > > anyway.
> >
> > Testing with sqlite3 and mysql4 shows that performance drastically
> > improves with writeback writeout.
>
>   And do you have the databases configured to use direct IO or not?

I don't think so, but these tests are only meant to expose the underlying 
problem which needs to be fixed, while this RFC proposes a useful 
workaround.

In another post Jan Kara wrote:
>   Hmm, if you're willing to test patches, then you could try a debug
> patch: http://bugzilla.kernel.org/attachment.cgi?id=14574
>   and send me the output. What kind of load do you observe problems with
> and which problems exactly?

8M-record insert into indexed db-table:
         ordered  writeback
sqlite3:  75m22s    8m45s
mysql4 :  23m35s    5m29s

Also, see the 'konqueror deadlocks in 2.6.22' thread.


Thanks!

--
Al

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