-----Original Message----- From: Bob Friesenhahn [mailto:bfrie...@simple.dallas.tx.us] Sent: 22. februar 2010 18:52
>> I updated and it looks good so far, but we will test it quite thoroughly. >> >> Just another quick question (or maybe a feature request): is there a >> safe way to apply a transform from several threads without locking? >> >> I guess I can create several transforms and call each from its own >> thread, but that may eat up a lot of memory when a large CMYK profile is >> used. > GraphicsMagick multithreads lcms transforms by creating a transform for each > thread. OpenMP is used for the threading. In most cases this provides a > very good speedup but I have noticed that certain types of profiles > (hopefully rare!) require quite a lot of time to create a transform, and > this causes a problem for performance if the image is not suitably large. >> We anticipate 16 to 32 cores in the not-too-distant-future, and we >> currently need to call cmsDoTransform() per line. I hate to take any >> kind of lock inside these calls :-/ > Definitely locking while using the transform is very bad. If the system > is NUMA (e.g. AMD Opteron) then there would be considerably more > performance if each worker thread created its own transform so that > allocated/initialized memory is "hot" and local for each thread. I found > that lcms1 did not allow that due to thread safety problems. > > What architecture does your not-too-distant-future hardware use? > > Bob Hi Bob, For the many-cores we are on standard AMD64: Windows and Mac. I think we would be OK with creating a transform per thread, but it seems particularly wasteful on multi-megabyte CMYK profiles. In most cases we only need to create a few transforms which can be reused, so I don't think this will kill us. But if we can get a better solution we will take it :-) Regards, Esben Høgh-Rasmussen Myosotis Software Engineer Phase One A/S Roskildevej 39 DK-2000 Frederiksberg Denmark Phone: + 45 36 13 12 07 Fax.: + 45 36 46 02 22 Mobile: + 45 28 51 10 79 E-mail: e...@phaseone.com www.phaseone.com ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Lcms-user mailing list Lcms-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lcms-user
