sensus ultra slow read

[Artur Wroblewski]

On Fri, Aug 3, 2012 at 8:10 AM, Jef Driesen <jefdriesen at telenet.be> wrote:
> On 2012-08-03 01:46, Artur Wroblewski wrote:
>>
>> I am using libdivecomputer 781f0db71f7a06591e819f7960dd5b504b4f16a0
>> at the moment and when trying to download the data from my
>> Sensus Ultra I can see the following on Linux via strace
>>
>> select(4, [3], [], [], {5, 0})          = 1 (in [3], left {4, 999992})
>> read(3, "\1\0\323u\245", 31095)         = 5
>> select(4, [3], [], [], {5, 0})          = 1 (in [3], left {4, 2265})
>> read(3, "\2\3d\35\321\202\n\7\2\0z\203\177", 31090) = 13
>> select(4, [3], [], [], {5, 0})          = 1 (in [3], left {4, 999869})
>> read(3, "\1\371\0\n\0W\4", 31077)       = 7
>> select(4, [3], [], [], {5, 0})          = 1 (in [3], left {4, 999995})
>> read(3, "\17\0\1", 31070)               = 3
>> select(4, [3], [], [], {5, 0})          = 1 (in [3], left {4, 999968})
>> read(3, "\0`@", 31067)                  = 3
>
>
> The behavior you see with strace is perfectly normal.
[...]

The select/read calls are normal of course, but the amount of bytes read
I consider as weird - seems like device is providing the data in quite slow
manner or the read call stops reading too fast.

>> The data download is very slow (still downloading actually ;) and I wonder
>> what that could be
>> - some change in libdivecomputer (it reads 1-5 bytes at once :/)
>> - the device dies
>> - Linux kernel 3.5.0
>> - combination of all above
>>
>> Does anyone experience something similar?
>
>
> Have you measured the download time?When I check an older logfile of mine
> (version c4172ecdf6c2f6b68eba7e06e446d46aef66a729), a full download (2080768
> bytes) took 206 seconds on my system. In a more recent logfile I have lying
> around (downloaded on 2012/06/28, don't know the exact version, but probably
> 87397a4ea1c63d78efd9bf751dee19f54257a6f9), it took only 186 seconds. So
> that's perfectly in line with the expected timings. Do you get very
> different numbers?

It took about 1h! In the past I was getting about 3 minutes.

I tried various versions of libdivecomputer as well (the above, 0.1.0 and
a217a0fb803bbb6ada1d298cd534ed2bb092b25b) and older kernel 3.3.0.

I am downloading all dives, but getting none of them. My previous data
dump contains 199 dives. :) This one shall have around 215. I have not
seen significant time degradation in the past.

Well, looks like device issue, I will take it diving and let's see if there will
be some improvement afterwards. ;)

Thanks for all the detailed explanation.

Best regards,

w