On Tue, 9 Nov 2010 16:28:02 +0900 (JST), KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> wrote: > So, I don't think application developers will use fadvise() aggressively > because we don't have a cross platform agreement of a fadvice behavior. > I strongly disagree. For a long time I have been trying to resolve interactivity issues caused by my rsync-based backup script. Many kernel developers have said that there is nothing the kernel can do without more information from user-space (e.g. cgroups, madvise). While cgroups help, the fix is round-about at best and requires configuration where really none should be necessary. The easiest solution for everyone involved would be for rsync to use FADV_DONTNEED. The behavior doesn't need to be perfectly consistent between platforms for the flag to be useful so long as each implementation does something sane to help use-once access patterns. People seem to mention frequently that there are no users of FADV_DONTNEED and therefore we don't need to implement it. It seems like this is ignoring an obvious catch-22. Currently rsync has no fadvise support at all, since using[1] the implemented hints to get the desired effect is far too complicated^M^M^M^Mhacky to be considered merge-worthy. Considering the number of Google hits returned for fadvise, I wouldn't be surprised if there were countless other projects with this same difficulty. We want to be able to tell the kernel about our useage patterns, but the kernel won't listen. Cheers, - Ben [1] http://insights.oetiker.ch/linux/fadvise.html -- 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>