VM Requirement Document - v0.0
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Quoted 9 lines
Windows NT/2000 has flags that can be for each CreateFile operation ("open" in Unix terms), for instance
FILE_ATTRIBUTE_TEMPORARY
FILE_FLAG_WRITE_THROUGH
FILE_FLAG_NO_BUFFERING
FILE_FLAG_RANDOM_ACCESS
FILE_FLAG_SEQUENTIAL_SCAN
There is a BSD-originated convention for this - madvise().
If you look in the Linux VM code there is a bit of explicit code for different madvise access patterns, but I'm not sure if it's 100% supported.
Drop-behind would be really, really nice to have for my multimedia applications. I routinely deal with very large video files (several times larger than my RAM). When I sequentially read though such files a bit at a time, I do NOT want the old pages sitting there in RAM while all of my other running programs are rudely paged out...
(hrm, maybe I could hack up my own manual read-ahead/drop-behind with mmap() and memory locking...)
Regards,
Dan
Quoted 2 lines · Dan Maas
(hrm, maybe I could hack up my own manual read-ahead/drop-behind with
mmap()and memory locking...)
Just to argue portability for a moment (portability on the expected results, that is, vs APIs).
Would this technique work across a variety of OSes?
Would the recent caching difficulties of the 2.4.* series have handled such a technique in a reasonable fashion?
mrc
Signature · 3 lines
Mike Castle [email protected] www.netcom.com/~dalgoda/ We are all of us living in the shadow of Manhattan. -- Watchmen fatal ("You are in a maze of twisty compiler features, all different"); -- gcc
Quoted 10 lines · Dan Maas
Quoted 9 lines
Windows NT/2000 has flags that can be for each CreateFile operation ("open" in Unix terms), for instance
FILE_ATTRIBUTE_TEMPORARY
FILE_FLAG_WRITE_THROUGH
FILE_FLAG_NO_BUFFERING
FILE_FLAG_RANDOM_ACCESS
FILE_FLAG_SEQUENTIAL_SCAN
We do (nearly) already have O_DIRECT which won't touch cache (alas I don't think I will read-ahead more)
Xav