Re: RFC on io-stalls patch

[Chris Mason <mason@suse.com>]

On Tue, 2003-07-15 at 04:28, Jens Axboe wrote:

> Definitely, because prepare to be a bit disappointed. Here are scores
> that include 2.4.21 as well:

> io_load:
> Kernel            [runs]        Time    CPU%    Loads   LCPU%   Ratio
> 2.4.21                 3        543     49.7    100.4   19.0    4.08
> 2.4.22-pre5            3        637     42.5    120.2   18.5    4.75
> 2.4.22-pre5-axboe      3        540     50.0    103.0   18.1    4.06

Huh, this is completely different than io_load on my box (2P scsi, ext3,
data=writeback)

io_load:
Kernel      [runs]      Time    CPU%    Loads   LCPU%   Ratio
2.4.21           3      520     52.5    27.8    15.2    3.80
2.4.22-pre5      3      394     69.0    21.5    15.4    2.90
2.4.22-sync      3      321     84.7    16.2    15.8    2.36

Where 2.4.22-sync was the variant I posted yesterday.  I don't really
see how 2.4.21 can get numbers as good as 2.4.22-pre5 on the io_load
test, the read starvation with a big streaming io is horrible.

The data=writeback is changing the workload significantly, I used it
because I didn't want the data=ordered code to flush all dirty buffers
every 5 seconds.  I would expect ext3 data=ordered to be pretty
starvation prone in 2.4.21 as well though.

BTW, the contest run times vary pretty wildy.  My 3 compiles with
io_load running on 2.4.21 were 603s, 443s and 515s.  This doesn't make
the average of the 3 numbers invalid, but we need a more stable metric.

-chris