Hi, Wu, Wu Fengguang wrote: >>>In adaptive readahead, the context based method may be of particular >>>interest to postgresql users. It works by peeking into the file cache >>>and check if there are any history pages present or accessed. In this >>>way it can detect almost all forms of sequential / semi-sequential read >>>patterns, e.g. >>> - parallel / interleaved sequential scans on one file >>> - sequential reads across file open/close >>> - mixed sequential / random accesses >>> - sparse / skimming sequential read >>> >>>It also have methods to detect some less common cases: >>> - reading backward >>> - seeking all over reading N pages Gread news, thanks! > This call will disable readahead totally for fd: > posix_fadvise(fd, any, any, POSIX_FADV_RANDOM); > > This one will reenable it: > posix_fadvise(fd, any, any, POSIX_FADV_NORMAL); > > This one will enable readahead _and_ set max readahead window to > 2*max_readahead_kb: > posix_fadvise(fd, any, any, POSIX_FADV_SEQUENTIAL); I think that this is an easy, understandable and useful interpretation of posix_fadvise() hints. Are there any rough estimates when this will get into mainline kernel (if you intend to submit)? Thanks, Markus -- Markus Schaber | Logical Tracking&Tracing International AG Dipl. Inf. | Software Development GIS Fight against software patents in EU! www.ffii.org www.nosoftwarepatents.org
