> Message du 16/04/19 09:40 > De : "Remco Viëtor" > A : "Jean-Luc CECCOLI" > Copie à : > Objet : Re: [darktable-user] Images order in db > > On lundi 15 avril 2019 22:29:56 CEST Jean-Luc CECCOLI wrote: > (...) > > Maybe, but even if it doesn't forget the article, having to go back and > > forth because the list doesn't follow the articles order must take more > > time than if it just had to pick them in one pass. > > > What does "125th, 43rd, 229th, 1st, 111th..." mean, in any case? > > > > I mean that instead of loading the files in sequence "1, 2, 3, 4, 5, etc.", > > as they do are on the disk (which I am certain, since I forced them to be > > copied in this order), they are loaded randomly. > (...) > If there's even the slightest latency between the end or reading one file and > the start of reading the next, the platter will have rotated too far to allow > reading to start as soon as the disk is ready for sequentially placed files. > That would introduce *extra* latency of the order of milliseconds... > > So a strict "in layout order" reading of a set of files is *not* the fastest > solution. > > As reading latencies are probably different from writing latencies (if only > due to the journalling most file systems do), even writing out the files in a > given order doesn't mean that order is fastest for reading. > > With respect to the database: Linux uses unused memory as disk buffers. So > even if the whole database isn't in the program's memory, there's a good > chance it will be in the disk buffers (for my 20+k files, the dt database > takes up ~50MB, compared to 16GB total RAM). In that case, database order of > images is *completely irrelevant* (as far as treatment speed is concerned), > as > any reads in there are pure memory to memory reads, no disk access required; > any required disk access to read image files will be several orders of > magnitude slower (say ms to µs). > > Remco > OK, I understand. Don't ask me why, but from the beginning, my resonment was the total opposite to what you explain here, which seems much more sensible. So, I'll let the app load the photos as it feels.
Rgrds, J.-Luc ____________________________________________________________________________ darktable user mailing list to unsubscribe send a mail to [email protected]
