i think just dev address
remap of bus is only done when you acess /uncached/bus.xxxx
or /uncached/
Em 30 de março de 2012 13:42, Ivan Lisenkov <[email protected]> escreveu:
> Thank you for your answer, many things come more clear.
>
> But I have one dumb question still. If I request
> /uncached/devaddress/value does owfs initiate search for all devices on a
> bus, or just devaddress?
> On Mar 27, 2012 11:41 PM, "Paul Alfille" <[email protected]> wrote:
>
>> Openfile and close file are essentially null operations in owfs under
>> FUSE.
>>
>> First off, there aren't any real files.
>> Second open and close are essentially ignored. It's only the read and
>> write that generate activity.
>>
>> I did some measurements using 4 different ways to access 1000 owfs
>> readings.
>>
>> 1. owread: (owserver --fake=10)
>>
>> #!/bin/sh
>> d=`/opt/owfs/bin/owdir | grep 10`
>> time for a in {0..999} ; do /opt/owfs/bin/owread /uncached$d/temperature
>> > /dev/null ; done
>>
>> real 0m2.428s
>> user 0m0.108s
>> sys 0m0.288s
>>
>> 2. owfs (owfs --fake=10 -m ~/1wire)
>>
>> #!/bin/sh
>> d=`dir -1 ~/1wire | grep 10`
>> time for a in {0..999} ; do cat ~/1wire/uncached/$d/temperature >
>> /dev/null ; done
>>
>> real 0m1.910s
>> user 0m0.092s
>> sys 0m0.296s
>>
>> 3. owhttpd (owhttpd --fake=10 -p 4444)
>>
>> #/bin/sh
>> d=`wget localhost:4444/ -q -O- | tr "<>" "\n\n" | grep "^10" | uniq`
>> time for a in {0..999} ; do wget localhost:4444/uncached/$d/temperature
>> -q -O/dev/null ; done
>>
>> real 0m4.152s
>> user 0m0.164s
>> sys 0m0.384s
>>
>> 4. perl (this program):
>>
>> #!/usr/bin/perl -w
>> use OW ;
>> OW::init("--fake=10");
>> for (split(',',OW::get("/")) ) {
>> if (m/^10/) {
>> my $d = $_ ;
>> for (0..999) {
>> OW::get($d."temperature") ;
>> }
>> exit 0 ;
>> }
>> }
>>
>> real 0m0.023s
>> user 0m0.012s
>> sys 0m0.008s
>>
>>
>>
>> Conclusion:
>> All these cases are with no real 1-wire activity, they only measure the
>> overhead ( of the loop and process creation)
>> Of the shell methods, the filesystem case is fastest, and the web server
>> is slowest, at least if accessed by a new invocation of wget for every call.
>>
>> Also note that the actual time per loop is 2-4 msec, so any method used
>> to get 1 second samples will have insignificant overhead costs.
>>
>> If we include the perl example (of any method where a persistent
>> connection to the library is kept and no independent processes need to be
>> launched for each reading), the overhead is 20 usec.
>>
>> Also note that all these examples would be a lot cleaner if the device
>> address were specified.
>>
>> Paul Alfille
>>
>> On Mon, Mar 26, 2012 at 5:35 PM, Roberto Spadim <[email protected]>wrote:
>>
>>> i think owhttp have a bug in setting values (any one) i don´t know if
>>> the newest version have this problem, please check, if its ok tell us,
>>> if not tell us too =)
>>>
>>> Em 26 de março de 2012 18:25, Ivan Lisenkov <[email protected]> escreveu:
>>> > Thank you for your answers!
>>> >
>>> > The problem with selective search is that I don't know if the device is
>>> > still on a bus or not, so polling on ordinary search is more reliable
>>> for
>>> > hardware failure detection. Second, alarm is set for sensed values,
>>> not for
>>> > latches, so it is possible to miss some very short event.
>>> >
>>> > I know, 1-wire is not the fastest network on the Earth, but I'm trying
>>> my
>>> > best :)
>>> >
>>> > PS.
>>> >
>>> > It seems it is not possible to set negative alarm values for DS18B20
>>> > temperature sensors. Or it is a bug in owhttp interface?
>>> >
>>> >
>>> > Best Regards,
>>> >
>>> > Ivan, PhD
>>> >
>>> >
>>> >
>>> >
>>> >
>>> > On Tue, Mar 27, 2012 at 12:13 AM, Serg Oskin <[email protected]> wrote:
>>> >>
>>> >> Try to use the alarm-directory.
>>> >>
>>> >> # Setup
>>> >> foreach 12.*
>>> >> openeach
>>> >> writevalue_to_set_alarm
>>> >> closeeach
>>> >> end foreach
>>> >>
>>> >> # Main loop
>>> >> foreach uncached/alarm
>>> >> openeach
>>> >> readvalue
>>> >> reset_alarm
>>> >> closeeach
>>> >> end loop
>>> >>
>>> >> --
>>> >> Serg.
>>> >>
>>> >> > Greetings to all,
>>> >> >
>>> >> > I am implementing a system which need to poll sensors (mainly
>>> DS2406 and
>>> >> > DS2408) nearly every second. Of course I use uncached values of
>>> sensors to
>>> >> > get the most recent data. I have about 15-20 sensors to poll.
>>> >> >
>>> >> > I see three options:
>>> >> >
>>> >> > First:
>>> >> > loop:
>>> >> > openfile("12.XXXXXXXX/latch.A");
>>> >> > readvalue;
>>> >> > closefile;
>>> >> > end loop.
>>> >> >
>>> >> > The most obvious one, but open/close file is rather costly
>>> operation.
>>> >> >
>>> >> > Second:
>>> >> > openfile("12.XXXXXXXX/latch.A");
>>> >> > loop:
>>> >> > readvalue;
>>> >> > goto_first_line;
>>> >> > end loop;
>>> >> > closefile;
>>> >> >
>>> >> > This is better, but is there some chance, that value will be cached
>>> >> > somewhere inside OS?
>>> >> >
>>> >> > Third:
>>> >> > give up on owfs and use owhttpd and make tcp connections to read
>>> files.
>>> >> >
>>> >> > I think this is a heaviest one, but crossplatform, so can be used on
>>> >> > windows. Can owhttpd have about 20 concurrent connections in a
>>> second?
>>> >> >
>>> >> >
>>> >> > What strategy to choose? Thank you for any help in advance.
>>> >> >
>>> >> >
>>> >> > Best Regards,
>>> >> >
>>> >> > Ivan, PhD
>>> >> >
>>> >> >
>>> >> >
>>> >> >
>>> >> >
>>> >> >
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>>> >> >
>>> >> >
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>>> >>
>>> >>
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>>>
>>>
>>> --
>>> Roberto Spadim
>>> Spadim Technology / SPAEmpresarial
>>>
>>>
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>>
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