Re: xfs: very slow after mount, very slow at umount

[Mark Lord <kernel@xxxxxxxxxxxx>]

On 11-01-27 10:40 AM, Justin Piszcz wrote:
> 
> 
> On Thu, 27 Jan 2011, Mark Lord wrote:
..
>> Can you recommend a good set of mkfs.xfs parameters to suit the 
>> characteristics
>> of this system?  Eg. Only a few thousand active inodes, and nearly all files 
>> are
>> in the 600MB -> 20GB size range.  The usage pattern it must handle is up to
>> six concurrent streaming writes at the same time as up to three streaming 
>> reads,
>> with no significant delays permitted on the reads.
>>
>> That's the kind of workload that I find XFS handles nicely,
>> and EXT4 has given me trouble with in the past.
..
> I did a load of benchmarks a long time ago testing every mkfs.xfs option there
> was, and I found that most of the time (if not all), the defaults were the 
> best.
..

I am concerned with fragmentation on the very special workload in this case.
I'd really like the 20GB files, written over a 1-2 hour period, to consist
of a very few very large extents, as much as possible.

Rather than hundreds or thousands of "tiny" MB sized extents.
I wonder what the best mkfs.xfs parameters might be to encourage that?

Cheers