On Tue, Nov 23, 2010 at 09:55:49AM -0500, Ben Gamari wrote: > On Tue, 23 Nov 2010 09:38:59 +0000, Mel Gorman <mel@xxxxxxxxx> wrote: > > > If it's mapped pagecache then the user was being a bit silly (or didn't > > > know that some other process had mapped the file). In which case we > > > need to decide what to do - leave the page alone, deactivate it, or > > > half-deactivate it as this patch does. > > > > > > > What are the odds of an fadvise() user having used mincore() in advance > > to determine if the page was in use by another process? I would guess > > "low" so this half-deactivate gives a chance for the page to be promoted > > again as well as a chance for the flusher threads to clean the page if > > it really is to be reclaimed. > > > Do we really want to make the user jump through such hoops as using > mincore() just to get the kernel to handle use-once pages properly? I would think "no" which is why I support half-deactivating pages so they won't have to. The downside is that it's essentially a race window as another process needs to reactivate the page before it gets reclaimed to avoid a major fault. > I hope the answer is no. I know that fadvise isn't supposed to be a > magic bullet, but it would be nice if more processes would use it to > indicate their access patterns and the only way that will happen is if > it is reasonably straightforward to use. > > - Ben > -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- 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>