linux-ext4 - Re: Test results for ext4

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Date:	Fri, 30 May 2008 13:12:39 -0500
From:	"Jose R. Santos" <jrs@...ibm.com>
To:	Valerie Clement <valerie.clement@...l.net>
Cc:	ext4 development <linux-ext4@...r.kernel.org>,
	Mingming Cao <cmm@...ibm.com>
Subject: Re: Test results for ext4

On Fri, 30 May 2008 17:50:43 +0200
Valerie Clement <valerie.clement@...l.net> wrote:

> Hi all,
> 
> Since a couple of weeks, I did batches of tests to have some
> performance numbers for the new ext4 features like uninit_groups,
> flex_bg or journal_checksum on a 5TB filesystem.
> I tried to test allmost all combinations of mkfs and mount options,
> but I put only a subset of them in the result tables, the most
> significant for me.
> 
> I had started to do these tests on a kernel 2.6.26-rc1, but I'd got
> several hangs and crashes occuring randomly outside ext4, sometimes
> in the slab code or in the scsi driver eg., and which were not
> reproductible. Since 2.6.26-rc2, no crash or hang occur with ext4 on
> my system.
> 
> The first results and the test description are available here:
> http://www.bullopensource.org/ext4/20080530/ffsb-write-2.6.26-rc2.html
> http://www.bullopensource.org/ext4/20080530/ffsb-readwrite-2.6.26-rc2.html
> 
> I will complete them in the next days.
> 
> In the first batch of tests, I compare the I/O throughput to create
> 1-GB files on disk in different configurations. The CPU usage is also
> given to show mainly how the delayed allocation feature reduces it.
> The average number of extents per file shows the impact of the
> multiblock allocator and the flex_bg grouping on the file
> fragmentation. At last, the fsck time shows how the uninit_groups
> feature reduces the e2fsck duration.
> 
> In the second batch of tests, the results show improvements in
> transactions -per-second throughput when doing small files writes,
> reads and creates when using the flex_bg grouping.
> The same ffsb test on an XFS filesystem hangs, I will try to have
> traces.
> 
> If you are interested in other tests, please let me know.

How about adding the following in "[filesystem0]" to age the filesystem:

        agefs=1
        [threadgroup0]
                num_threads=10
                write_size=40960
                write_blocksize=4096
                create_weight=10
                append_weight=10
                delete_weight=1
        [end0]
                desired_util=0.80

This will age the filesystem until it reaches 80% utilization before
starting the benchmark.  Since a 5TB disk will take a while to age, I
suggest trying this on just a few runs.

> 
>    Valérie
> 

-JRS
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