|TIFF and LibTiff Mailing List Archive|
LibTiff Mailing List
2016.01.29 15:49 "Re: OpenMP enabled libtiff", by Aaron Boxer
On Fri, Jan 29, 2016 at 10:48 AM, Aaron Boxer <firstname.lastname@example.org> wrote: > > > On Fri, Jan 29, 2016 at 9:46 AM, Bob Friesenhahn < > email@example.com> wrote: > >> On Fri, 29 Jan 2016, Aaron Boxer wrote: >> >>> >>> Thanks. This is exactly the work flow I am interested in : tens of >>> thousands of ~10 MB TIFFs, accessed >>> sequentially. Only 4 files would be open at a given time. So, even >>> though the files get closed, are you >>> suggesting I will see swapping in this case ? >>> >> >> It would not be true swapping or paging-out (actually, there could be >> some paging out to swap), but there will be memory pressure since memory >> mapping behaves as a cache. The file data is still in memory (by default) >> after the file has been unmapped and memory pages are re-claimed (existing >> contents forgotten, and page re-purposed) for new activity based on new >> memory pressures, and the time the memory has remained inactive. >> >> The actual behavior is highly OS implementation dependent. >> >> On Unix type systems, the madvise() function can be used to help control >> behavior of memory-mapped data (e.g. MADV_DONTNEED), but again behavior is >> highly OS implementation dependent and the only way to know for sure is to >> test. >> >> > Thanks, Bob. On windows, since there is no madvise function, wouldn't > reading a file and memory mapping the file both give the same result: the > file gets cached in the OS file cache, causing memory pressure > when the cache gets filled up ? > By reading, I mean using the fopen/fread interface, vs memory mapping.