Let me try that again:
Your current setup is something like:
owget -> owserver -> bus master
If you add another layer:
owget -> owserver -> owserver -> bus master
you can see the effect of the owserver layer.
OWFS doesn't care how many owserver layers you add, so adding several
layers might help seeing very small timing increments.
For that matter, timing a single owget call may show more the effect
of starting the owget program and be very influenced by the filesystem
buffers.
Here is an example:
# 1 level owserver:
sudo /opt/owfs/bin/owserver -u -p 4401
# time 100 directory listings
time \
for x in 0 1 2 3 4 5 6 7 8 9 ; do for y in 0 1 2 3 4 5 6 7 8 9 ; do \
/opt/owfs/bin/owdir -s 4401 /uncached > /dev/null ; \
done ; done
real 0m14.791s
user 0m0.010s
sys 0m0.030s
# 10 level owserver:
sudo /opt/owfs/bin/owserver -u -p 4401
/opt/owfs/bin/owserver -s 4401 -p 4402
/opt/owfs/bin/owserver -s 4402 -p 4403
/opt/owfs/bin/owserver -s 4403 -p 4404
/opt/owfs/bin/owserver -s 4404 -p 4405
/opt/owfs/bin/owserver -s 4405 -p 4406
/opt/owfs/bin/owserver -s 4406 -p 4407
/opt/owfs/bin/owserver -s 4407 -p 4408
/opt/owfs/bin/owserver -s 4408 -p 4409
/opt/owfs/bin/owserver -s 4409 -p 4410
# again time 100 directory listings all through the 10 layers:
time \
for x in 0 1 2 3 4 5 6 7 8 9 ; do for y in 0 1 2 3 4 5 6 7 8 9 ; do \
/opt/owfs/bin/owdir -s 4410 /uncached > /dev/null ; \
done ; done
real 0m15.517s
user 0m0.000s
sys 0m0.050s
Hence my point that it's the 1-wire bus, rather than owserver communication.
To show the point even more dramatically, if we ask for the statistics
directory, which is all in memory, we get:
#1 layer
time \
for x in 0 1 2 3 4 5 6 7 8 9 ; do for y in 0 1 2 3 4 5 6 7 8 9 ; do \
/opt/owfs/bin/owdir -s 4401 /uncached/statistics > /dev/null ; \
done ; done
real 0m0.255s
user 0m0.020s
sys 0m0.010s
#10 layers -- note that we have to ask for the distal bus specifically.
time \
for x in 0 1 2 3 4 5 6 7 8 9 ; do for y in 0 1 2 3 4 5 6 7 8 9 ; do \
/opt/owfs/bin/owdir -s 4410
/uncached/bus.0/bus.0/bus.0/bus.0/bus.0/bus.0/bus.0/bus.0/bus.0/bus.0/statistics
> /dev/null ; \
done ; done
real 0m1.095s
user 0m0.000s
sys 0m0.040s
Which adds about the same absolute overhead for owserver communication.
Thus my conclusion that there may be delays or inefficiency in our
implementation, but it isn't owserver and you need to substract out
program (owget) setup time.
Paul Alfille
On Sun, Jan 23, 2011 at 12:39 PM, Guil Barros <[email protected]> wrote:
> Hi Paul,
> I'm not entirely sure what you mean, could you elaborate?
>
> Thanks,
> -Guil
>
> On Sun, Jan 23, 2011 at 6:11 AM, Paul Alfille <[email protected]> wrote:
>> On Sat, Jan 22, 2011 at 10:26 PM, Guil Barros <[email protected]> wrote:
>>> I am doing a number of reads with owget on individual DS18B20's and
>>> DS2438's and not quite getting the performance I expect:
>>> I assume this is at least partially overhead related to the owserver
>>> comms, is there a better way to handle multiple device access with the
>>> owshell commands? Anything I can do to speed things up otherwise?
>>>
>>
>> Can you test by going through 2 layers of owserver? That will show the
>> owserver overhead. Very small in my prior tests.
>>
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