Thanks Steve, Fair enough!
Richard On Thu, Sep 17, 2015 at 8:20 PM, Stephen Woodbridge <wood...@swoodbridge.com> wrote: > Richard, > > I have already imbedded OSRM into a C++ application and in fact wrapped that > application into a postgresql database extension. I my case I only need data > for a city but I was making literally billions of calls to osrm. > > As Patrick said, OSRM makes random access calls to memory and there are a > lot of variables that come into play like how well the data is clustered in > memory pages, how many page faults you hit, etc. For your specific use case > no one will have a good answer for you and you really need to do some > performance testing using the product the way you intend it to be used and > see what the performance issues are. Maybe you use case is fine. The OSRM > public service uses lots of memory because it has to support multiple random > requests anywhere in the world and it can not afford to get stuck page in > swap. Using swap and an SSD might be fine in your application, and may be it > won't, but we do not have enough information to consider the problem more > than to give the standard answer - more memory is faster more swapping is > slower. > > -Steve > > > > > On 9/17/2015 8:45 PM, Richard Marsden wrote: >> >> Thanks for the quick reply Patrick. >> >>> Presumably I could do the same for world preparation & routing? Have, >>> perhaps a 100GB+ swap file, ideally on an SSD. >> >> >>> This will fall apart when you have some actual load pressure on the >>> system. We need random access to memory, which will create a lot of >>> page faults (== slow). Even an SSD is not even close to memory speed. >> >> >>> You have two options: >>> split the datasets >>> get a bigger server >> >> >> >> I would imagine that is the case for the standard http server. I was >> thinking of using it as a linked library from a C++ program. Splitting >> the datasets by continent is a possibility though. >> >> (writing a C# interface was another thought, but that would be a >> different use case and definitely with smaller datasets) >> >> Cheers, >> >> Richard >> >> >> >> >> On Thu, Sep 17, 2015 at 4:37 PM, Patrick Niklaus >> <patrick.nikl...@student.kit.edu> wrote: >>> >>> W.r.t. the pre-preprocessing you are correct. >>> >>>> What is that extra power used for? >>> >>> >>> Including all sorts of external data sources. Also the logic in the >>> lua profiles is not just replaceable by simple key-value pairs, OSM >>> requires you to handle a lot of special cases. >>> >>>> Presumably I could do the same for world preparation & routing? Have, >>>> perhaps a 100GB+ swap file, ideally on an SSD. >>> >>> >>> This will fall apart when you have some actual load pressure on the >>> system. We need random access to memory, which will create a lot of >>> page faults (== slow). Even an SSD is not even close to memory speed. >>> >>> You have two options: >>> - split the datasets >>> - get a bigger server >>> >>> Cheers, >>> Patrick >>> >>> >>> On Thu, Sep 17, 2015 at 10:06 PM, Richard Marsden <winw...@gmail.com> >>> wrote: >>>> >>>> I've been evaluating OSRM, using it primarily as a library from C++. >>>> >>>> I believe I've determined the answer to most of the questions, but I'm >>>> also looking for confirmation. >>>> (I understand the reason for these constraints - the trade-off of >>>> speed vs flexibility) >>>> >>>> First, road speeds are set with 'profile.lua' at the osrm-extract >>>> stage. This filters out unnecessary roads (eg. foot paths for car >>>> routing), but also applies the road speeds. >>>> If I wish to change the speed profile, I need to regenerate the road >>>> network with osrm-extract and osrm-routed. >>>> Correct? >>>> >>>> If I wanted different speeds for the final distance/time calculations, >>>> I could use the returned route, and apply my own speed table according >>>> to the road type of each road segment. This would not, of course, >>>> change the route geometry is calculated. >>>> >>>> If I want a shortest route (distance optimized) instead of a quickest >>>> route (time optimized), I need to set all the road speeds to the same >>>> speed and regenerate the network. I.e. osrm does not directly support >>>> the concept of a "shortest route". >>>> >>>> The profile is provided with a LUA file. I had to look this one up :-) >>>> Looks a useful scripting language, but why is this profile a script >>>> file, and not a simple configuration file of constants (eg. key-value >>>> pairs)? >>>> Seems like an unnecessary complexity - I'd like to understand the >>>> perceived advantages. What is that extra power used for? >>>> >>>> Finally, the memory usage... I saw a reference to the server requiring >>>> 40GB of memory for pan-European routing. Presumably that could be >>>> offset with a large swap file(?) >>>> A large swap file has worked well when I was testing the US-South >>>> region on an 8GB machine. >>>> Presumably I could do the same for world preparation & routing? Have, >>>> perhaps a 100GB+ swap file, ideally on an SSD. >>>> >>>> >>>> Cheers, >>>> >>>> Richard Marsden >>>> >>>> _______________________________________________ >>>> OSRM-talk mailing list >>>> OSRM-talk@openstreetmap.org >>>> https://lists.openstreetmap.org/listinfo/osrm-talk >>> >>> >>> _______________________________________________ >>> OSRM-talk mailing list >>> OSRM-talk@openstreetmap.org >>> https://lists.openstreetmap.org/listinfo/osrm-talk >> >> >> _______________________________________________ >> OSRM-talk mailing list >> OSRM-talk@openstreetmap.org >> https://lists.openstreetmap.org/listinfo/osrm-talk >> > > > _______________________________________________ > OSRM-talk mailing list > OSRM-talk@openstreetmap.org > https://lists.openstreetmap.org/listinfo/osrm-talk _______________________________________________ OSRM-talk mailing list OSRM-talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/osrm-talk
