HD to SSD question.

[Mihai T. Lazarescu]

On Mon, Aug 19, 2013 at 09:24:14PM +0200, Heinz Diehl wrote:

> On 19.08.2013, Mihai T. Lazarescu wrote: 
> 
> > It appears that CFQ can sense and adapt to SSD and has little
> > if any loss to other I/O schedulers:
> 
> > http://www.velobit.com/storage-performance-blog/bid/126135/Effects-Of-Linux-IO-Scheduler-On-SSD-Performance
> 
> They only tested bandwidth, not latency.  On my systems,
> deadline outperforms cfq, both wrt bandwidth *and* latency,
> both felt and measured.  Latency is especially sensible when
> there's a lot of disk I/O. You can do some testing using
> Ted Tso's fsync-tester:
> 
> https://oss.oracle.com/~mason/fsync-tester.c

Thanks for the pointer.  I add to the mix my test results for
F19 with kernel 3.10.7 on an ASUS UX31E with its factory 256GB
SSD-only mass storage.

CFQ scheduler run1:
    write time: 0.0007s fsync time: 0.9397s
    write time: 0.0004s fsync time: 5.6349s
    write time: 0.0004s fsync time: 1.1586s
    write time: 0.0004s fsync time: 14.4159s
    write time: 0.0004s fsync time: 12.7619s
    write time: 0.0004s fsync time: 13.5689s

CFQ scheduler run2:
    write time: 0.0010s fsync time: 0.9970s
    write time: 0.0004s fsync time: 5.7953s
    write time: 0.0004s fsync time: 0.9726s
    write time: 0.0004s fsync time: 14.9300s
    write time: 0.0005s fsync time: 0.7052s
    write time: 0.0004s fsync time: 8.3616s
    write time: 0.0004s fsync time: 2.1200s
    write time: 0.0004s fsync time: 4.5161s

Deadline scheduler run1:
    write time: 0.0007s fsync time: 1.6141s
    write time: 0.0005s fsync time: 11.2728s
    write time: 0.0005s fsync time: 18.5445s
    write time: 8.0272s fsync time: 23.0132s

Deadline scheduler run2:
    write time: 0.0137s fsync time: 0.9517s
    write time: 0.0005s fsync time: 11.5287s
    write time: 0.0005s fsync time: 17.4877s
    write time: 0.0005s fsync time: 12.9626s
    write time: 0.0004s fsync time: 56.6898s

Noop scheduler run1:
    write time: 0.0062s fsync time: 1.2807s
    write time: 0.0005s fsync time: 11.4450s
    write time: 0.0005s fsync time: 18.3745s
    write time: 7.6150s fsync time: 25.1109s

Noop scheduler run2:
    write time: 0.0099s fsync time: 1.3952s
    write time: 0.0004s fsync time: 11.3167s
    write time: 0.0004s fsync time: 19.0572s
    write time: 7.4895s fsync time: 25.1773s

Mihai