> > I've recently been trying to track down the root cause of my server's > > persistent issue of thrashing horribly after being left inactive. It > > seems that the issue is likely my nightly backup schedule (using rsync) > > which traverses my entire 50GB home directory. I was surprised to find > > that rsync does not use fadvise to notify the kernel of its use-once > > data usage pattern. > > > > It looks like a patch[1] was written (although never merged, it seems) > > incorporating fadvise support, but I found its implementation rather > > odd, using mincore() and FADV_DONTNEED to kick out only regions brought > > in by rsync. It seemed to me the simpler and more appropriate solution > > would be to simply flag every touched file with FADV_NOREUSE and let the > > kernel manage automatically expelling used pages. > > > > After looking deeper into the kernel implementation[2] of fadvise() the > > reason for using DONTNEED became more apparant. It seems that the kernel > > implements NOREUSE as a noop. A little googling revealed[3] that I not > > the first person to encounter this limitation. It looks like a few > > folks[4] have discussed addressing the issue in the past, but nothing > > has happened as of 2.6.36. Are there plans to implement this > > functionality in the near future? It seems like the utility of fadvise > > is severely limited by lacking support for NOREUSE. > > btw, Other OSs seems to also don't implement it. > example, I've heared other OSs status of fadvise() from private mail. NetBSD: no-op (as linux) FreeBSD/DragonflyBSD/OpenBSD: don't exist posix_fadvise(2) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>