On Sat, 16 Feb 2013 14:53:43 +1030 Rusty Russell <rusty@xxxxxxxxxxxxxxx> wrote: > Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> writes: > > On Fri, 15 Feb 2013 18:13:04 -0500 > > Johannes Weiner <hannes@xxxxxxxxxxx> wrote: > >> I dunno. The byte vector might not be optimal but its worst cases > >> seem more attractive, is just as extensible, and dead simple to use. > > > > But I think "which pages from this 4TB file are in core" will not be an > > uncommon usage, and writing a gig of memory to find three pages is just > > awful. > > Actually, I don't know of any usage for this call. That's good news ;) We shouldn't add it unless there's damn good reason. > I'd really like to use it for backup programs, so they stop pulling > random crap into memory (but leave things already resident). But that > needs to madvise(MADV_DONTNEED) on the page, so need mmap. > > So why not just use mincore? One can use fadvise(POSIX_FADV_DONTNEED) to drop the pages. Or toss your backup app into a small memcg so it reclaims its own stuff. See recent thread "mm: fadvise: Drain all pagevecs if POSIX_FADV_DONTNEED fails to discard all pages" -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>