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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